rc.io:Add USE_IO == yes && IO_PRESENT == yes test

  On a FMU without a px4io (FMUv4, NXPhlite etc), this code should
  not be run.

ROMFS/px4fmu_common/init.d/rc.io

@@ -2,15 +2,17 @@
 #
 # PX4IO interface init script.
 #
-
-if px4io start
+if [ $USE_IO == yes -a $IO_PRESENT == yes ]
 then
-	# Allow PX4IO to recover from midair restarts.
-	px4io recovery
-
-	# Adjust PX4IO update rate limit.
-	px4io limit 400
-else
-	echo "PX4IO start failed" >> $LOG_FILE
-	tune_control play -m ${TUNE_ERR}
+	if px4io start
+	then
+		# Allow PX4IO to recover from midair restarts.
+		px4io recovery
+	
+		# Adjust PX4IO update rate limit.
+		px4io limit 400
+	else
+		echo "PX4IO start failed" >> $LOG_FILE
+		tune_control play -m ${TUNE_ERR}
+	fi
 fi