lockd: Eliminate harmless mixed sign comparison in nlmdbg_cookie2a()

The cookie->len field is unsigned, so the loop index variable in
nlmdbg_cookie2a() should also be unsigned.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/lockd/xdr.c b/fs/lockd/xdr.c
index 633653b..3e459e1 100644
--- a/fs/lockd/xdr.c
+++ b/fs/lockd/xdr.c
@@ -612,8 +612,7 @@
 	 * called with BKL held.
 	 */
 	static char buf[2*NLM_MAXCOOKIELEN+1];
-	int i;
-	int len = sizeof(buf);
+	unsigned int i, len = sizeof(buf);
 	char *p = buf;
 
 	len--;	/* allow for trailing \0 */