ROMFS: fix SYS_USE_IO==0

When SYS_USE_IO was disabled, px4io would not start and thus there was no
RC. SYS_USE_IO=0 is interesting on Quads to avoid the IO and reduce output
latency.

Tested on Pixhawk 1 and Pixhawk 4

ROMFS/px4fmu_common/init.d/rc.interface

@@ -125,6 +125,11 @@ then
 	set MIXER_AUX none
 fi
 
+if [ $USE_IO == no ]
+then
+	set MIXER_AUX none
+fi
+
 if [ $MIXER_AUX != none -a $AUX_MODE != none ]
 then
 	#

ROMFS/px4fmu_common/init.d/rcS

@@ -321,8 +321,6 @@ then
 
 	set IO_PRESENT no
 
-	if [ $USE_IO == yes ]
-	then
 	#
 	# Check if PX4IO present and update firmware if needed
 	#
@@ -369,12 +367,11 @@ then
 	fi
 	unset IO_FILE
 
-		if [ $IO_PRESENT == no ]
+	if [ $USE_IO == yes -a $IO_PRESENT == no ]
 	then
 		echo "PX4IO not found" >> $LOG_FILE
 		tune_control play -m ${TUNE_ERR}
 	fi
-	fi
 
 	#
 	# Set default output if not set