px4fmu_common:Add passivly starting the PWM rgbled driver

   Board builds may now inclulde both the PWM and I2C RGB LED
   To add the PWM RGB LED driver:The board must define
   BOARD_HAS_LED_PWM and include rgbled_pwm the moulde list.

   This change attempts to start the PWM rgbled driver, that
   may or may not be present. If it is not present the +e
   setting allows the start up to continue.

ROMFS/px4fmu_common/init.d/rcS

@@ -140,6 +140,10 @@ then
 		fi
 	fi
 
+	# FMUv5 may have both PWM I2C RGB LED support
+
+	rgbled_pwm start
+
 	# Currently unused, but might be useful down the road
 	#if pca8574 start
 	#then