Adds support for V4L2_CID_HFLIP and V4L2_CID_VFLIP to allow
flipping the image.

The driver previously enabled H & V flips in the register table,
therefore the controls default to the same settings to avoid
changing the behaviour.
Signed-off-by: Dave Stevenson <dave.stevenson@raspberrypi.com>
Reviewed-by: Jacopo Mondi <jacopo@jmondi.org>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>