[media] MAINTAINERS: remove myself as a maintainer of VEU and VOU V4L2 drivers

Since I'm currently unable to dedicate sufficient time to the maintainership
of these two drivers update their status to "orphan" until new maintainers
appear.

Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>