msm: mdss: Add DDC support for HDMI Tx driver

Display Data Channel, DDC, is responsible for transmitting
EDID and HDCP information between HDMI sink and HDMI Tx controller.
Add support for this in HDMI Tx driver.

Change-Id: I58d10c61277d36425d89a2270f0ad0495ffd3a1f
Signed-off-by: Ujwal Patel <ujwalp@codeaurora.org>