PX4 System:Expunge the nuttx adc structure from the system

This PR is preliminary ground work for FMUv5.

   PX4 does not use the NuttX adc driver. But used the same format
   for the data returned by the nuttx ADC driver.

   There was a fixme:in src/platforms/px4_adc.h "this needs to be
   a px4_adc_msg_s type" With this PR the need for
   src/platforms/px4_adc.h goes away as the driver drv_adc.h now
   describes the px4_adc_msg_t.

src/platforms/posix/drivers/adcsim/adcsim.cpp

@@ -42,7 +42,6 @@
 
 #include <px4_config.h>
 #include <px4_time.h>
-#include <px4_adc.h>
 #include <board_config.h>
 #include <drivers/device/device.h>
 
@@ -84,7 +83,7 @@ private:
 	perf_counter_t		_sample_perf;
 
 	unsigned		_channel_count;
-	adc_msg_s		*_samples;		/**< sample buffer */
+	px4_adc_msg_t	*_samples;		/**< sample buffer */
 
 	/** worker function */
 	virtual void		_measure();
@@ -119,7 +118,7 @@ ADCSIM::ADCSIM(uint32_t channels) :
 		}
 	}
 
-	_samples = new adc_msg_s[_channel_count];
+	_samples = new px4_adc_msg_t[_channel_count];
 
 	/* prefill the channel numbers in the sample array */
 	if (_samples != nullptr) {
@@ -145,7 +144,7 @@ ADCSIM::~ADCSIM()
 ssize_t
 ADCSIM::devRead(void *buffer, size_t len)
 {
-	const size_t maxsize = sizeof(adc_msg_s) * _channel_count;
+	const size_t maxsize = sizeof(px4_adc_msg_t) * _channel_count;
 
 	if (len > maxsize) {
 		len = maxsize;
@@ -204,7 +203,7 @@ test()
 	}
 
 	for (unsigned i = 0; i < 50; i++) {
-		adc_msg_s data[12];
+		px4_adc_msg_t data[PX4_MAX_ADC_CHANNELS];
 		ssize_t count = h.read(data, sizeof(data));
 
 		if (count < 0) {

src/platforms/posix/include/system_config.h

@@ -39,6 +39,11 @@
 
 #pragma once
 
+#define ADC_BATTERY_VOLTAGE_CHANNEL     10
+#define ADC_BATTERY_CURRENT_CHANNEL     ((uint8_t)(-1))
+#define ADC_AIRSPEED_VOLTAGE_CHANNEL    11
+#define ADCSIM0_DEVICE_PATH	"/dev/adc0"
+
 /*
  * I2C busses
  */

src/platforms/px4_adc.h

@@ -1,67 +0,0 @@
-/****************************************************************************
- *
- *   Copyright (c) 2014 PX4 Development Team. All rights reserved.
- *
- * Redistribution and use in source and binary forms, with or without
- * modification, are permitted provided that the following conditions
- * are met:
- *
- * 1. Redistributions of source code must retain the above copyright
- *    notice, this list of conditions and the following disclaimer.
- * 2. Redistributions in binary form must reproduce the above copyright
- *    notice, this list of conditions and the following disclaimer in
- *    the documentation and/or other materials provided with the
- *    distribution.
- * 3. Neither the name PX4 nor the names of its contributors may be
- *    used to endorse or promote products derived from this software
- *    without specific prior written permission.
- *
- * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
- * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
- * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
- * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
- * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
- * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
- * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
- * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
- * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
- * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
- * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
- * POSSIBILITY OF SUCH DAMAGE.
- *
- ****************************************************************************/
-
-/**
- * @file px4_adc.h
- *
- * ADC header depending on the build target
- */
-
-#pragma once
-
-#include <stdint.h>
-
-#if defined(__PX4_ROS)
-#error "ADC not supported in ROS"
-#elif defined(__PX4_NUTTX)
-/*
- * Building for NuttX
- */
-#include <nuttx/analog/adc.h>
-#elif defined(__PX4_POSIX)
-
-// FIXME - this needs to be a px4_adc_msg_s type
-// Curently copied from NuttX
-struct adc_msg_s {
-	uint8_t      am_channel;               /* The 8-bit ADC Channel */
-	int32_t      am_data;                  /* ADC convert result (4 bytes) */
-} __attribute__((packed));
-
-// Example settings
-#define ADC_BATTERY_VOLTAGE_CHANNEL     10
-#define ADC_BATTERY_CURRENT_CHANNEL     ((uint8_t)(-1))
-#define ADC_AIRSPEED_VOLTAGE_CHANNEL    11
-#define ADCSIM0_DEVICE_PATH	"/dev/adc0"
-#else
-#error "No target platform defined"
-#endif