msm: mdss: hdmi: adjust HDMI DDC speed configuration

HDMI 2.0 compliance E-DDC test requires the DDC
signal timings to meet a minimum threshold to pass
the compliance test. Current DDC settings were not
matching the requirement.

Adjust the DDC settings to meet the threshold and
also make sure to leave the remaining bits of DDC
speed register untouched.

Change-Id: I9a33ba38baa8be94dee5447e79ad0a3a2a0bc8be
Signed-off-by: Narender Ankam <nankam@codeaurora.org>