drm/ili9225: Call MIPI DBI mode_valid helper

MIPI DBI drivers validate each mode against their native resolution.
Add this test to ili9225.

Signed-off-by: Thomas Zimmermann <tzimmermann@suse.de>
Reviewed-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://patchwork.freedesktop.org/patch/msgid/20221202125644.7917-3-tzimmermann@suse.de