ALSA: hda - Implement path-based power filter to the generic parser

This patch adds a better power filter hook for powering down unused
widgets in the generic parser.

The feature is enabled by setting hda_gen_spec.power_down_unused
flag.

Signed-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/hda_generic.h

@@ -211,6 +211,7 @@ struct hda_gen_spec {
 	unsigned int add_stereo_mix_input:1; /* add aamix as a capture src */
 	unsigned int add_out_jack_modes:1; /* add output jack mode enum ctls */
 	unsigned int add_in_jack_modes:1; /* add input jack mode enum ctls */
+	unsigned int power_down_unused:1; /* power down unused widgets */
 
 	/* other internal flags */
 	unsigned int no_analog:1; /* digital I/O only */