aerofc: Implement ADC

Measure the battery voltage of Aero RTF kit will be done by FPGA
and read by AeroFC using I2C bus.

The protocol is a little bit odd, it have different I2C slave
address for each "register", in future the FPGA RTL will
have a protocol more similar to other I2C sensors.

Also Aero RTF don't have a ADC line to measure current consumption.

ROMFS/px4fmu_common/init.d/rc.sensors

@@ -52,8 +52,13 @@ else
 	fi
 fi
 
-if adc start
+if ver hwcmp AEROFC_V1
 then
+	# Aero FC uses separate driver
+else
+	if adc start
+	then
+	fi
 fi
 
 if ver hwcmp AUAV_X21
@@ -344,6 +349,10 @@ then
 	if hmc5883 -X start
 	then
 	fi
+
+	if aerofc_adc start
+	then
+	fi
 fi
 
 if meas_airspeed start