media: mediatek: vcodec: decoder: Fix 4K frame size enumeration

This partially reverts commit b018be06 ("media: mediatek: vcodec:
Read max resolution from dec_capability"). In this commit, the maximum
resolution ended up being a function of both the firmware capability and
the current set format.

However, frame size enumeration for output (coded) formats should not
depend on the format set, but should return supported resolutions for
the format requested by userspace.

Fix this so that the driver returns the supported resolutions correctly,
even if the instance only has default settings, or if the output format
is currently set to VP8F, which does not support 4K.

This adds an copy of special casing for !VP8 and 4K support. The other
existing copy will be removed when .max_{width,height} are removed from
|struct mtk_vcodec_ctx| in a subsequent patch.

Fixes: b018be06 ("media: mediatek: vcodec: Read max resolution from dec_capability")
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Tested-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>