drm/tidss: Annotate dma-fence critical section in commit path

Ends right after hw_done(), totally standard case.

Acked-by: Jyri Sarha <jsarha@ti.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Jyri Sarha <jsarha@ti.com>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210121152959.1725404-12-daniel.vetter@ffwll.ch