[media] media: lirc_dev: change irctl->attached to be a boolean

The "attached" member of struct irctl is a boolean value, so let the code
reflect that.

Signed-off-by: David Härdeman <david@hardeman.nu>
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>