drm: Drop ARCH_MULTIPLATFORM from dependencies

Some of these dependencies used to be sensible when only a small part of
the platforms supported by ARCH=arm could be compiled together in a
single kernel image. Nowadays ARCH_MULTIPLATFORM is only used as a guard
for kernel options incompatible with a multiplatform image. See commit
84fc8636 ("ARM: make ARCH_MULTIPLATFORM user-visible") for some more
details.

Signed-off-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Javier Martinez Canillas <javierm@redhat.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20221209220555.3631364-1-u.kleine-koenig@pengutronix.de