drm/msm: fix re-entry problem for msm_atomic_commit

When plane is detached from crtc in one atomic commit and then
attached to another crtc in the next atomic commit, the second
plane state swap will happen when the first commit is still running
in the previous crtc's worker thread, which will result in two
threads programming the same plane and run into undeterministic
state.

Fix is to add plane_mask check before state swap, together with
crtc_mask check. This will make sure there is no pending worker
thread working on the same plane.

Change-Id: I64cd4b68fa9746e988d933069ac0f8083d974c79
Signed-off-by: Xiaowen Wu <wxiaowen@codeaurora.org>