media: MAINTAINERS: Fix files for obsolete SoC camera framework

The SoC camera was moved to the staging tree but we missed updating
MAINTAINERS. Do that now.

Fixes: 280de94a ("media: soc_camera: Move to the staging tree")

Reported-by: Joe Perches <joe@perches.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>