netiucv: allow multiple interfaces to same peer

The NETIUCV device driver allows to connect a Linux guest on z/VM to
another z/VM guest based on the z/VM communication facility IUCV.
Multiple output paths to different guests are possible, as well as
multiple input paths from different guests.
With this feature, you can configure multiple point-to-point NETIUCV
interfaces between your Linux on System z instance and another z/VM
guest.
Signed-off-by: Ursula Braun <ursula.braun@de.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>