staging/fwserial: Create loop device the 'tty' way

Register a second tty driver to create loopback devices for
each firewire node. Note that the loopback devices are numbered
from 0; the tty->index is transformed when used to index the
port table.

Remove the hack that previously enabled this.

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>