media: hantro: Support NV12 on the G2 core

The G2 decoder block produces NV12 4x4 tiled format (NV12_4L4).
Enable the G2 post-processor block, in order to produce regular NV12.

The logic in hantro_postproc.c is leveraged to take care of allocating
the extra buffers and configure the post-processor, which is
significantly simpler than the one on the G1.

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>