ALSA: enable concurrent digital outputs for ALC1200

Add the SPDIF pin as slave digital out to enable concurrent
HDMI/SPDIF outputs for ASUS M3A-H/HDMI with ALC1200 codec.

Tested-by: Thomas Schneider <nailstudio@gmx.net>
Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_local.h b/sound/pci/hda/hda_local.h
index ec687b2..4086491 100644
--- a/sound/pci/hda/hda_local.h
+++ b/sound/pci/hda/hda_local.h
@@ -229,6 +229,7 @@
 	hda_nid_t hp_nid;	/* optional DAC for HP, 0 when not exists */
 	hda_nid_t extra_out_nid[3];	/* optional DACs, 0 when not exists */
 	hda_nid_t dig_out_nid;	/* digital out audio widget */
+	hda_nid_t *slave_dig_outs;
 	int max_channels;	/* currently supported analog channels */
 	int dig_out_used;	/* current usage of digital out (HDA_DIG_XXX) */
 	int no_share_stream;	/* don't share a stream with multiple pins */