ASoC: hdmi-codec: Add an op to set callback function for plug event

Add an op in hdmi_codec_ops so codec driver can register callback
function to handle plug event.

Driver in DRM can use this callback function to report connector status.

Signed-off-by: Cheng-Yi Chiang <cychiang@chromium.org>
Link: https://lore.kernel.org/r/20190717083327.47646-2-cychiang@chromium.org


Reviewed-by: Tzung-Bi Shih <tzungbi@google.com>
Signed-off-by: Mark Brown <broonie@kernel.org>