disp: msm: dp: add support for continuous PPS command

Add support to send PPS command with every frame for DP.
This is needed to satisfy the requirement of certain bridge
chips which need the PPS to be sent every frame.

Change-Id: I8711dff41e60d8b1e1c515a5d34a370a2409ce14
Signed-off-by: Abhinav Kumar <abhinavk@codeaurora.org>
Signed-off-by: Sudarsan Ramesh <sudarame@codeaurora.org>