NFS: Squelch compiler warning in decode_getdeviceinfo()

Clean up.

.../linux/nfs-2.6/fs/nfs/nfs4xdr.c: In function ‘decode_getdeviceinfo’:
.../linux/nfs-2.6/fs/nfs/nfs4xdr.c:5008: warning: comparison between signed and unsigned integer expressions
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

fs/nfs/nfs4xdr.c

@@ -5000,7 +5000,7 @@ static int decode_getdeviceinfo(struct xdr_stream *xdr,
 		goto out_overflow;
 	len = be32_to_cpup(p);
 	if (len) {
-		int i;
+		uint32_t i;
 
 		p = xdr_inline_decode(xdr, 4 * len);
 		if (unlikely(!p))