drm: msm: add skip_ddc support for hdmi display

HDMI display on auto boards has disabled pluggable function
and hardcoded 1080p mode for output. So ddc related function
should also be skipped. Otherwise, some error messages are
printed when accessing ddc.

Change-Id: I42694b0586dd870e7881b422cd3d6ee960276b17
Signed-off-by: Suprith Malligere Shankaregowda <supgow@codeaurora.org>
Signed-off-by: Guchun Chen <guchunc@codeaurora.org>