msm: mdss: use post init delay in pan display path

Use Post init delay in pan display path to maintain the uniformity as
used in display kickoff to control the delay for backlight update.

Change-Id: Iaee041b14be558fcf651de259597dc3c0b25841b
Signed-off-by: Raghavendra Ambadas <rambad@codeaurora.org>