media: MAINTAINERS: add Petr Cvek as a maintainer for the ov9640 driver

The soc_camera drivers are marked as orphaned. Add Petr Cvek as a new
maintainer for ov9640 driver after its switch from the soc_camera.

Signed-off-by: Petr Cvek <petrcvekcz@gmail.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>