media: hantro: add initial SAMA5D4 support

The SoC features a Hantro G1 compatible video decoder, supporting the
MPEG-2, VP8 and H264 codecs with resolutions up-to 1280x720.

Post-processing core is also available on the SoC.

Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
Signed-off-by: Emil Velikov <emil.velikov@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>