ASoC: codecs: add support for WCD939x Codec

Merge series from Neil Armstrong <neil.armstrong@linaro.org>:

Add the main WCD9390/WCD9395 Audio Codec driver to support:
- 4 ADC inputs for up to 5 Analog Microphones
- 4 DMIC inputs for up to 8 Digital Microphones
- 4 Microphone BIAS
- Stereo Headphone output
- Mono EAR output
- MBHC engine for Headset Detection

This adds:
- bindings
- MBHC changes to support Type-C muc
- Soundwire Slave driver
- Code driver

The USB Mux subsystem support will be submitted separately
since it's a functionally separate subsystem connected over
I2C with it's own reset signal.