media: v4l2-ctrl: Add control to enable h.264 constrained intra prediction

Allow to enable h.264 constrained intra prediction (macroblocks using
intra prediction modes are not allowed to use residual data and decoded
samples of neighboring macroblocks coded using inter prediction modes).
This control directly corresponds to the constrained_intra_pred_flag
field in the h.264 picture parameter set.

Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>