media: v4l2-ctrls: Add new V4L2_H264_DECODE_PARAM_FLAG_P/BFRAME flags

Add new V4L2_H264_DECODE_PARAM_FLAG_P/BFRAME flags that are needed by
NVIDIA Tegra video decoder. Userspace will have to set these flags in
accordance to the type of a decoded frame.

Reviewed-by: Nicolas Dufresne <nicolas@collabora.com>
Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>