ALSA: wss: convert CS4231 mixer to dB scale

Convert CS4231 mixer to dB scale after AD1848 mixer.

Also, add missing microphone boost control for the AD1848
and correct wrong bits for loopback volume on the AD1848.

Signed-off-by: Krzysztof Helt <krzysztof.h1@wp.pl>
Signed-off-by: Takashi Iwai <tiwai@suse.de>