[ALSA] Add dB information to es1938 driver

Added the dB information to ESS Solo (es1938) driver.
The new compound dB range TLVs are used for non-linear native
volume controls.

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