drm/amd/display: Handle commit plane with no FB.

1) Always call flip ISR, for any surface comit, not only for page flip.

2) For events not signaled in flip ISR, handle them in end of commit_tail.

3)Fix race condition between subsequent atomic calls by removing
  current state access AFTER drm_atomic_helper_commit_hw_done
  was called. After this call a pending next commit will
  swap in his own state into objects and proceed.

Signed-off-by: Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>
Reviewed-by: Harry Wentland <Harry.Wentland@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>