drm/msm/atomic: Drop per-CRTC locks in reverse order

lockdep dislikes seeing locks unwound in a non-nested fashion.

Fixes: b3d91800

 ("drm/msm: Fix race condition in msm driver with async layer updates")
Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Abhinav Kumar <abhinavk@codeaurora.org>