af_iucv: Add automatic (source) iucv_name to bind

If a socket is bound to an address using before calling connect
it is usual to leave it to the network system to choose an appropriate
outgoing application name respective port address.
af_iucv on VM uses a counter and uses simple numbers as unique identifiers.
This behaviour was missing when af_iucv is used with HiperSockets.

This patch contains a simple approach to harmonize af_iucv's behaviour.

Signed-off-by: Philipp Hachtmann <phacht@linux.vnet.ibm.com>
Signed-off-by: Frank Blaschka <blaschka@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>