When dealing with interlaced frames, reference lists must tell if
each particular reference is meant for top or bottom field. This info
is currently not provided at all in the H264 related controls.

Change reference lists to hold a structure, which specifies
an index into the DPB array and the field/frame specification
for the picture.

Currently the only user of these lists is Cedrus which is just compile
fixed here. Actual usage of will come in a following commit.
Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Signed-off-by: Ezequiel Garcia <ezequiel@collabora.com>
Tested-by: Jonas Karlman <jonas@kwiboo.se>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>