Add PM4125 audio codec driver

Add PM4125 audio codec driver

Merge series from Alexey Klimov <alexey.klimov@linaro.org>:

PMICs like PM4125 have in-built audio codec IC. The series here
adds support for this codec driver: DT bindings and codec driver
itself that consists mainly of two parts: soundwire devices and
codec part itself.

This audio codec can be found on platforms like QCM2290 and
on Qualcomm QRB2210 RB1 board.

We are working on this together with Srini
(srinivas.kandagatla@oss.qualcomm.com or srini@kernel.org).

This driver also has a bit limited support for concurrent playback,
since line out path is connected to left input channel.