ASoC: WM8770: Initial driver

The WM8770 is a high performance, multi-channel audio
codec.  The WM8770 is ideal for surround sound processing
applications for home hi-fi, automotive and other audio
visual equipment.

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