media: ov2680: rename ov2680_v4l2_init() to ov2680_v4l2_register()

The function not only does initialization but also registers the subdevice
so change its name to make this more clear.

Signed-off-by: Javier Martinez Canillas <javierm@redhat.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>