Introduce two new functions so that the API for lirc_dev matches that
of the rc-core and input subsystems.

This means that lirc_dev structs are managed using the usual four
functions:

lirc_allocate_device
lirc_free_device
lirc_register_device
lirc_unregister_device

The functions are pretty simplistic at this point, later patches will put
more flesh on the bones of both.
Signed-off-by: David Härdeman <david@hardeman.nu>
Signed-off-by: Sean Young <sean@mess.org>