The V4L2Capability has helpers to interogate the capabilities
of a device.
V4L2VideoDevice::enumPixelformats accesses the raw capabilites to check
if the device is supported by a MediaController device.
Provide a helper, and update the usage.
Reviewed-by: Naushir Patuck <naush@raspberrypi.com>
Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Signed-off-by: Kieran Bingham <kieran.bingham@ideasonboard.com>