niu.c: Use correct length in strncmp

Untested, no hardware

Signed-off-by: Joe Perches <joe@perches.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/niu.c b/drivers/net/niu.c
index 44558fc..8ce58c4 100644
--- a/drivers/net/niu.c
+++ b/drivers/net/niu.c
@@ -8143,7 +8143,7 @@
 	int i;
 
 	for (i = 0; i < len - 5; i++) {
-		if (!strncmp(s + i, "FCode ", 5))
+		if (!strncmp(s + i, "FCode ", 6))
 			break;
 	}
 	if (i >= len - 5)