drm/msm/hdmi: remove CONFIG_OF checks

We now only care about kernels that support DT. Remote the non-DT stuff.
While we're at it, use of_device_get_match_data to retrieve match data.

Signed-off-by: Archit Taneja <architt@codeaurora.org>
Signed-off-by: Rob Clark <robdclark@gmail.com>