media: hantro: vp9: add support for legacy register set

Some older G2 cores uses slightly different register set for HEVC and
VP9. Since vast majority of registers and logic is the same, it doesn't
make sense to introduce another drivers.

Add legacy_regs quirk and implement only VP9 changes for now. HEVC
changes will be introduced later, if needed.

Reviewed-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>