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>