ASoC: cs42l42: Add SoundWire support

Merge series from Stefan Binding <sbinding@opensource.cirrus.com>:

The CS42L42 has a SoundWire interface for control and audio. This
chain of patches adds support for this.

Patches #1 .. #5 split out various changes to the existing code that
are needed for adding Soundwire. These are mostly around clocking and
supporting the separate probe and enumeration stages in SoundWire.

Patches #6 .. #8 actually adds the SoundWire handling.