disp: msm: sde: add spinlocks to handle_frame_done call

By adding spin locks around the handle frame done, a race
condition, between the wait for idle of one frame, and the pp
done of the next frame, is mitigated.

Change-Id: I78650fc9688b22db6d314b9bed023e0ddad20dbf
Signed-off-by: Nilaan Gunabalachandran <ngunabal@codeaurora.org>