V4L2: H264 profile & level ctrls, FPS control and auto exp pri

Several control handling updates.
H264 profile and level controls.
Timeperframe/FPS reworked to add V4L2_CID_EXPOSURE_AUTO_PRIORITY to
select whether AE is allowed to override the framerate specified.

Signed-off-by: Dave Stevenson <dsteve@broadcom.com>