auhal: always set audio device callback

Previously, the audio device callback was only set when you call probe.
But in the case you reload the module (for example when switching from
encoded to unencoded output over the UI menu) probe was not called again.
This resulted in a crash when we want to delete the callback while closing.
Signed-off-by: Felix Paul Kühne <fkuehne@videolan.org>
(cherry picked from commit 0f62e1ad)
Signed-off-by: Jean-Baptiste Kempf <jb@videolan.org>

modules/audio_output/auhal.c

@@ -249,6 +249,9 @@ static int Open( vlc_object_t * p_this )
         goto error;
     }
 
+    /* If we change the device we want to use, we should renegotiate the audio chain */
+    var_AddCallback( p_aout, "audio-device", AudioDeviceCallback, NULL );
+
     /* Check for Digital mode or Analog output mode */
     if( AOUT_FMT_SPDIF( &p_aout->format ) && b_supports_digital )
     {
@@ -1033,9 +1036,6 @@ static void Probe( audio_output_t * p_aout )
         var_Set( p_aout, "audio-device", val );
     }
 
-    /* If we change the device we want to use, we should renegotiate the audio chain */
-    var_AddCallback( p_aout, "audio-device", AudioDeviceCallback, NULL );
-
     /* Attach a Listener so that we are notified of a change in the Device setup */
     err = AudioObjectAddPropertyListener( kAudioObjectSystemObject, &audioDevicesAddress, HardwareListener, (void *)p_aout );
     if( err )