drm: msm: Add ASoC generic hdmi audio codec support.

This patch adds support to generic audio codec via
ASoC hdmi-codec infrastucture which is merged recently.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
[rebased on efc9194b

]
Signed-off-by: Rob Clark <robdclark@gmail.com>