drm: renesas: shmobile: Use media bus formats in platform data

Replace the custom shmob_drm_interface enumeration values with standard
media bus formats.  This simplifies driver handling of bus formats and
prepares for DT support.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://lore.kernel.org/r/0a15e5100ca30d14953c93550eb1d4c2e18de939.1694767209.git.geert+renesas@glider.be