media: platform: mtk-mdp3: fix Kconfig dependencies

The new mdp3 driver uses 'select' to force-enable a couple of drivers
it depends on. This is error-prone and likely to cause dependency
loops as well as warnings like:

WARNING: unmet direct dependencies detected for VIDEO_MEDIATEK_VPU
  Depends on [n]: MEDIA_SUPPORT [=m] && MEDIA_PLATFORM_SUPPORT [=y] && MEDIA_PLATFORM_DRIVERS [=y] && V4L_MEM2MEM_DRIVERS [=n] && VIDEO_DEV [=m] && (ARCH_MEDIATEK [=y] || COMPILE_TEST [=y])
  Selected by [m]:
  - VIDEO_MEDIATEK_MDP3 [=m] && MEDIA_SUPPORT [=m] && MEDIA_PLATFORM_SUPPORT [=y] && MEDIA_PLATFORM_DRIVERS [=y] && (MTK_IOMMU [=m] || COMPILE_TEST [=y]) && VIDEO_DEV [=m] && (ARCH_MEDIATEK [=y] || COMPILE_TEST [=y]) && HAS_DMA [=y] && REMOTEPROC [=y]

This specific warning was already addressed in a previous patch,
but there are similar unnecessary 'select' statements, so turn those
into 'depends on'. This also means the dependency on ARCH_MEDIATEK
is redundant and can be dropped.

Fixes: 61890cca ("media: platform: mtk-mdp3: add MediaTek MDP3 driver")
Fixes: 9195a860 ("media: platform: mtk-mdp3: remove unused VIDEO_MEDIATEK_VPU config")
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>