[ALSA] hda-codec - Fix STAC922x capture boost level

STAC922x provides the capture boost level up to 4, but actually it
works only up to 2.  Since the range of the mixer is automatically
defined from amp-capability bits, we need to override the value
beforehand.  snd_hda_override_amp_caps() is introduced for this
purpose.
The function patch_stac922x() calls this for NID 0x12 (Mux Capture
Volume).  This should fix another recording problem on Intel Macs.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>