tipc: remove redundant 'peer_name' field in struct tipc_sock

The field 'peer_name' in struct tipc_sock is redundant, since
this information already is available from tipc_port, to which
tipc_sock has a reference.

We remove the field, and ensure that peer node and peer port
info instead is fetched via the functions that already exist
for this purpose.

Signed-off-by: Jon Maloy <jon.maloy@ericsson.com>
Reviewed-by: Ying Xue <ying.xue@windriver.com>
Reviewed-by: Erik Hugne <erik.hugne@ericsson.com>
Signed-off-by: David S. Miller <davem@davemloft.net>