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/svcsubs.c b/fs/lockd/svcsubs.c
index 9e4d6aab..ad478da 100644
--- a/fs/lockd/svcsubs.c
+++ b/fs/lockd/svcsubs.c
@@ -417,7 +417,7 @@
 static int
 nlmsvc_match_ip(void *datap, struct nlm_host *host)
 {
-	return nlm_cmp_addr(nlm_srcaddr(host), datap);
+	return rpc_cmp_addr(nlm_srcaddr(host), datap);
 }
 
 /**