ASoC: google: dt-bindings: add new compatible for sc7180-coachz

Add devicetree bindings for coachz in documentation file

Signed-off-by: xuyuqing <xuyuqing@huaqin.corp-partner.google.com>
Link: https://lore.kernel.org/r/20201112014328.695232-2-xuyuqing@huaqin.corp-partner.google.com


Signed-off-by: Mark Brown <broonie@kernel.org>