media: hantro: Add quirk for NV12/NV12_4L4 capture format

The G2 core decoder engine produces NV12_4L4 format,
which is a simple NV12 4x4 tiled format. The driver currently
hides this format by always enabling the post-processor engine,
and therefore offering NV12 directly.

This is done without using the logic in hantro_postproc.c
and therefore makes it difficult to add VP9 cleanly.

Since fixing this is not easy, add a small quirk to force
NV12 if HEVC was configured, but otherwise declare NV12_4L4
as the pixel format in imx8mq_vpu_g2_variant.dec_fmts.

This will be used by the VP9 decoder which will be added soon.

Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Andrzej Pietrasiewicz <andrzej.p@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>