media: uapi: v4l2-core: Add sensor ancillary data V4L2 foucc type.

Add V4L2_META_FMT_SENSOR_DATA format 4CC.

This new format will be used by the BCM2835 Unicam device to return
out camera sensor embedded data.

Signed-off-by: Naushir Patuck <naush@raspberrypi.com>