tipc: simplify signature of tipc_find_service()

We reduce the signature of tipc_find_service() and
tipc_create_service(). The reason for doing this might not
be obvious, but we plan to let struct tipc_uaddr contain
information that is relevant for these functions in a later
commit.

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>