media: ipu3-cio2: Add T: entry to MAINTAINERS

Development for the ipu3-cio2 driver is taking place in media_tree, but
there's no T: entry in MAINTAINERS to denote that - rectify that oversight

Reviewed-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Daniel Scally <djrscally@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>