tipc: refactor tipc_sendmsg() and tipc_lookup_anycast()

We simplify the signature if function tipc_nametbl_lookup_anycast(),
using address structures instead of discrete integers.

This also makes it possible to make some improvements to the functions
__tipc_sendmsg() in socket.c and tipc_msg_lookup_dest() in msg.c.

Signed-off-by: Jon Maloy <jmaloy@redhat.com>
Acked-by: Ying Xue <ying.xue@windriver.com>
Acked-by: Hoang Le <hoang.h.le@dektech.com.au>
Acked-by: Tung Nguyen <tung.q.nguyen@dektech.com.au>
Acked-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>