[media] rc-main: Fix device de-registration logic

rc unregister logic were deadly broken, preventing some drivers to
be removed. Among the broken things, rc_dev_uevent() is being called
during device_del(), causing a data filling on an area that it is
not ready anymore.

Also, some drivers have a stop callback defined, that needs to be called
before data removal, as it stops data polling.

Acked-by: Jarod Wilson <jarod@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>