ASoC: dt-bindings: cros_ec_codec: add SHM bindings

- Add "reg" for binding to shared memory exposed by EC.
- Add "memory-region" for binding to memory region shared by AP.

Acked-by: Rob Herring <robh@kernel.org>
Acked-by: Benson Leung <bleung@chromium.org>
Signed-off-by: Tzung-Bi Shih <tzungbi@google.com>
Link: https://lore.kernel.org/r/20191017213539.06.I0df85fe54162426e31f60a589d9b461c65df2faa@changeid


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