ASoC: Add WM8350 AudioPlus codec driver

The WM8350 is an integrated audio and power management subsystem which
provides a single-chip solution for portable audio and multimedia systems.

The integrated audio CODEC provides all the necessary functions for
high-quality stereo recording and playback. Programmable on-chip
amplifiers allow for the direct connection of headphones and microphones
with a minimum of external components. A programmable low-noise bias
voltage is available to feed one or more electret microphones.
Additional audio features include programmable high-pass filter in the
ADC input path.

This driver was originally written by Liam Girdwood with further updates
from me.

Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>