ASoC: add es8316 codec driver

Add a codec driver for the Everest ES8316, based on code provided by
David Yang from Everest Semi.

I limited the functionality to items where the vendor code was clear,
and things that can be tested on the Weibu F3C (Intel Cherry Trail).
As a result the initial implementation only supports running in slave
mode at single speed (up to 48kHz sample rate) using I2S. HPD is not
supported.

Signed-off-by: David Yang <yangxiaohua@everest-semi.com>
[drake@endlessm.com: significant cleanups and simplifications,
                     remove dead/unclear code]
Signed-off-by: Daniel Drake <drake@endlessm.com>
Signed-off-by: Mark Brown <broonie@kernel.org>