media: rkvdec-h264: Add field decoding support

This makes use of the new feature in the reference builder to program
up to 32 references when doing field decoding. It also signals the
parity (top or bottom) of the field to the hardware.

Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Reviewed-by: Sebastian Fricke <sebastian.fricke@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>