ASoC: codecs: jz4725b: Various improvements and fixes

Merge series from Siarhei Volkau <lis8215@gmail.com>:

The patchset fixes:
 - Line In path stays powered off during capturing or
   bypass to mixer.
 - incorrectly represented dB values in alsamixer, et al.
 - incorrect represented Capture input selector in alsamixer
   in Playback tab.
 - wrong control selected as Capture Master

The patchset improves:
 - Exposes output stage (post mixer) gain control and makes it new
   Master playback gain, DAC gain was the previous master.
   However, no Master mute now.
 - Exposes all mixer inputs (both Mics, LineIn and DAC) with their
   gain controls.
 - Exposes microphones widgets: single/differential input, boost.

Known issues:
 - Bypass path enablement isn't applied immediately, for make
   things going bit clock needs to be triggered for a bit,
   e.g. by aplay dummy.wav
   It might be a hardware bug, since the bit clock isn't
   declared as required for codec operation.

Tested on:
 - Ritmix RZX-27 (jz4725b).
 - Ritmix RZX-50 (jz4755).