TTY: ircomm, define carrier routines

These will be used by the tty_port wait_til_ready later. (Now they are
used by our code.)

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Samuel Ortiz <samuel@sortiz.org>
Cc: netdev@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>