X25 fix dead unaccepted sockets

1, An X25 program binds and listens
2, calls arrive waiting to be accepted
3, Program exits without accepting
4, Sockets time out but don't get correctly cleaned up
5, cat /proc/net/x25/socket shows the dead sockets with bad inode fields.

This line borrowed from AX25 sets the dying socket so the timers clean up later.

Signed-off-by: Andrew Hendry <andrew.hendry@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>