drm/msm/dsi-staging: update dsi pclk timing calculation

Update dsi pclk timing calculation based on hardware
recommended settings. Command mode panels need to account
for margin and video mode panels only uses DSC compression
on horizontal active region.

Change-Id: I9c1b8d85ad1f3079e1e8549d192f8293d7cfe299
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>