Revert "drm/radeon/audio: don't set speaker allocation on DCE4+"

This reverts commit 555b1b651a.

Let's try this again for 3.13.  It's required for proper
interaction with alsa.  Was disabled previously in 3.12
to be on the safe side since it caused problems on older
asics.

drivers/gpu/drm/radeon/dce6_afmt.c

@@ -156,9 +156,6 @@ void dce6_afmt_write_speaker_allocation(struct drm_encoder *encoder)
 	u8 *sadb;
 	int sad_count;
 
-	/* XXX: setting this register causes hangs on some asics */
-	return;
-
 	if (!dig->afmt->pin)
 		return;