tipc: eliminate redundant lookups in registry

As an artefact from the native interface, the message sending functions
in the port takes a port ref as first parameter, and then looks up in
the registry to find the corresponding port pointer. This despite the
fact that the only currently existing caller, tipc_sock, already knows
this pointer.

We change the signature of these functions to take a struct tipc_port*
argument, and remove the redundant lookups.

We also remove an unmotivated extra lookup in the function
socket.c:auto_connect(), and, as the lookup functions tipc_port_deref()
and ref_deref() now become unused, we remove these two functions.

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>