Move the tone_alarm driver out of the NuttX configs area and add it as an stm32-specific driver in the PX4 apps space.

Add a new tone_alarm command that can be used to start/stop alarm tones from the shell.

ROMFS/scripts/rcS

@@ -20,6 +20,11 @@
 set MODE autostart
 set USB autoconnect
 
+#
+# Start playing the startup tune
+#
+tone_alarm start
+
 #
 # Try to mount the microSD card.
 #
@@ -31,9 +36,6 @@ else
 	echo "[init] no microSD card found"
 fi
 
-usleep 500
-
-
 #
 # Look for an init script on the microSD card.
 #