ALSA: hda - Fix missing path between aamix and outputs in AD codecs

AD1988 family and AD1882 codecs have another mixer widget (0x21)
between the analog-loopback mixer widget (0x20) and the actual
outputs.  Due to this hole, the analog-loopbacks aren't sent properly
to the output pins.

As a band-aid fix, introduce another fields holding the aamix merge
path, and activate it.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_generic.h b/sound/pci/hda/hda_generic.h
index 980707f..d226856 100644
--- a/sound/pci/hda/hda_generic.h
+++ b/sound/pci/hda/hda_generic.h
@@ -107,6 +107,7 @@
 	hda_nid_t adc_nids[AUTO_CFG_MAX_INS];
 	hda_nid_t dig_in_nid;		/* digital-in NID; optional */
 	hda_nid_t mixer_nid;		/* analog-mixer NID */
+	hda_nid_t mixer_merge_nid;	/* aamix merge-point NID (optional) */
 	const char *input_labels[HDA_MAX_NUM_INPUTS];
 	int input_label_idxs[HDA_MAX_NUM_INPUTS];
 
@@ -163,6 +164,7 @@
 	int digout_paths[AUTO_CFG_MAX_OUTS];
 	int input_paths[HDA_MAX_NUM_INPUTS][AUTO_CFG_MAX_INS];
 	int loopback_paths[HDA_MAX_NUM_INPUTS];
+	int loopback_merge_path;
 	int digin_path;
 
 	/* auto-mic stuff */