media: MAINTAINERS: Add reviewer to vimc driver

After practically re-writing the driver to collpase it into a monolith,
I am adding myself as a reviewer for vimc driver.

Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>
Acked-by: Helen Koike <helen.koike@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>