Place v4l2_mbus_pixelcode in a #ifndef __KERNEL__ section so that kernel
users don't have access to these definitions.

We have to keep this definition for user-space users even though they're
encouraged to move to the new media_bus_format enum.
Signed-off-by: NBoris Brezillon <boris.brezillon@free-electrons.com>
Acked-by: NSakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: NHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: NMauro Carvalho Chehab <mchehab@osg.samsung.com>