remove all <cmath> usage

* the NuttX c++ library is incomplete, let's avoid including it until we have a real standard library in place

src/drivers/linux_pwm_out/linux_pwm_out.cpp

@@ -36,7 +36,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include <cmath>
+#include <math.h>
 
 #include <px4_platform_common/tasks.h>
 #include <px4_platform_common/getopt.h>

src/drivers/snapdragon_pwm_out/snapdragon_pwm_out.cpp

@@ -37,7 +37,7 @@
 #include <px4_platform_common/getopt.h>
 #include <px4_platform_common/posix.h>
 #include <errno.h>
-#include <cmath>	// NAN
+#include <math.h>	// NAN
 #include <string.h>
 
 #include <uORB/Subscription.hpp>

src/drivers/tap_esc/tap_esc.cpp

@@ -40,7 +40,7 @@
 #include <px4_platform_common/posix.h>
 #include <errno.h>
 
-#include <cmath>	// NAN
+#include <math.h>	// NAN
 #include <cstring>
 
 #include <lib/mathlib/mathlib.h>

src/drivers/uavcan/sensors/baro.cpp

@@ -37,7 +37,7 @@
 
 #include <drivers/drv_hrt.h>
 #include "baro.hpp"
-#include <cmath>
+#include <math.h>
 
 const char *const UavcanBarometerBridge::NAME = "baro";
 

src/drivers/uavcan/uavcan_drivers/kinetis/driver/src/uc_kinetis_clock.cpp

@@ -9,7 +9,7 @@
 
 #if UAVCAN_KINETIS_TIMER_NUMBER
 # include <cassert>
-# include <cmath>
+# include <math.h>
 
 /*
  * Timer instance

src/drivers/uavcan/uavcan_drivers/stm32/driver/src/uc_stm32_clock.cpp

@@ -9,7 +9,7 @@
 #if UAVCAN_STM32_TIMER_NUMBER
 
 #include <cassert>
-#include <cmath>
+#include <math.h>
 
 /*
  * Timer instance