BugLink: https://launchpad.net/bugs/420578

The OR has verified that his hardware distorts because of the 0 dB
offset not corresponding to the highest PCM level. Fix this by capping
said PCM level to 0 dB similarly to what we do for CX20549 (Venice).
Reported-by: Mike Pontillo <pontillo@gmail.com>
Tested-by: Mike Pontillo <pontillo@gmail.com>
Cc: <stable@kernel.org>
Signed-off-by: Daniel T Chen <crimsun@ubuntu.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>