mdss: hdmi: Disabling software DDC requests

Disable software DDC request before moving to
part3 of HDCP authentication and re-enable it on
before reading EDID. This is done to avoid any
DDC bus arbitration issues while handing over from
software DDC control to hardware DDC control.

Change-Id: Iffde0147e497c1411d867c22c3674b73ceb95bac
CRs-Fixed: 484366
Signed-off-by: Abhishek Kharbanda <akharban@codeaurora.org>