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>