hci_unregister_dev cannot fail and always returns 0. The drivers already ignore
the return value so we can safely make it return void.
Signed-off-by: NDavid Herrmann <dh.herrmann@googlemail.com>
Acked-by: NMarcel Holtmann <marcel@holtmann.org>
Signed-off-by: NGustavo F. Padovan <padovan@profusion.mobi>