media: lirc: do not call close() or open() on unregistered devices

If a lirc chardev is held open after a device is unplugged, rc_close()
will be called after rc_unregister_device(). The driver is not expecting
any calls at this point, and the iguanair driver causes an oops in
this scenario.

rc_open() can be called when the device is removed too, by calling open
on the chardev whilst the device is being removed.

Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>