sunrpc: add routine for comparing addresses

lockd needs these sort of routines, as does the NFSv4 callback code.

Move lockd's routines into common code and rename them so that they can
be used by others.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Acked-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
diff --git a/fs/lockd/mon.c b/fs/lockd/mon.c
index 30c9331..f956651 100644
--- a/fs/lockd/mon.c
+++ b/fs/lockd/mon.c
@@ -209,7 +209,7 @@
 	struct nsm_handle *nsm;
 
 	list_for_each_entry(nsm, &nsm_handles, sm_link)
-		if (nlm_cmp_addr(nsm_addr(nsm), sap))
+		if (rpc_cmp_addr(nsm_addr(nsm), sap))
 			return nsm;
 	return NULL;
 }