media: venus: add support for key frame

When client requests for a keyframe, set the property
to hardware to generate the sync frame.

Signed-off-by: Malathi Gottam <mgottam@codeaurora.org>
Acked-by: Tomasz Figa <tfiga@chromium.org>
Acked-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>