staging: mrst: Fix zorder handling while overlay updates are pending

staging: mrst: Fix zorder handling while overlay updates are pending

Configuring the Z order may potentially need to touch both overlays
simultaneosly. So ovl_wait() needs to be performed for both overlays.
Do that before touching any state to allow set_plane_opts() to fail
in a clean fashion.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Acked-by: Pauli Nieminen <pauli.nieminen@linux.intel.com>
Reviewed-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>