ALSA: hda - Allow aamix as a capture source

Since some codecs can choose the aamix as a capture source, we should
support it as well.  When spec->add_stereo_mix_input flag is set, the
parser checks the availability of aamix as the input source, and adds
the paths automatically when possible.

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 1763e33..89683c7 100644
--- a/sound/pci/hda/hda_generic.h
+++ b/sound/pci/hda/hda_generic.h
@@ -190,6 +190,7 @@
 	unsigned int vmaster_mute_enum:1; /* add vmaster mute mode enum */
 	unsigned int indep_hp:1; /* independent HP supported */
 	unsigned int indep_hp_enabled:1; /* independent HP enabled */
+	unsigned int add_stereo_mix_input:1; /* add aamix as a capture src */
 
 	/* loopback mixing mode */
 	bool aamix_mode;