disp: msm: sde: fix race condition in scheduler idle function

Currently driver reads CTL status register before checking
pending kickoff counter. This can lead to a register access
violation when there is a race condition between the ESD and
commit thread.

This change checks pending kickoff counter before reading
CTL status register.

Change-Id: I5828b580c16d075df19eb349ee88d8b7da47941e
Signed-off-by: Amine Najahi <anajahi@codeaurora.org>