msm: mdss: Dynamically change writeback path OT

Writeback path when used for WFD is processed at 1px/clk
whereas when used for rotator, it is processed at 4px/clk.
To ensure that writeback during WFD doesn't slow down,
reduce the WB block rotator OT to different number depending
on different target.

Change-Id: I6f37557756d0c8c5037bbd251637ed872d872f74
Signed-off-by: Jayant Shekhar <jshekhar@codeaurora.org>