disp: msm: sde: Initialize wr_ptr_wait_success after kickoff

wr_ptr_wait_success is true only if wr_ptr interrupt arrives, so
initialize it after display kickoff.

Change-Id: I5790d9dac25352898ece160f6b258b50ca2edefa
Signed-off-by: Ray Zhang <rayz@codeaurora.org>