drm: renesas: shmobile: Atomic conversion part 3

Complete the conversion to atomic mode setting by converting the
connector, and setting the DRIVER_ATOMIC flag.

Reviewed-by: Laurent Pinchart <laurent.pinchart+renesas@ideasonboard.com>
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/042f9ff076c4b1c87235c74c8b76c9d161e126ec.1694767209.git.geert+renesas@glider.be