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