netdev: use ARRAY_SIZE() instead of sizeof(array) / ETH_GSTRING_LEN

Using ARRAY_SIZE() on arrays of the form array[][K] makes it unnecessary
to know the value of K when checking its size.

Signed-off-by: Alejandro Martinez Ruiz <alex@flawedcode.org>
Signed-off-by: Jeff Garzik <jeff@garzik.org>
diff --git a/drivers/net/e1000/e1000_ethtool.c b/drivers/net/e1000/e1000_ethtool.c
index b83ccce..2e44191 100644
--- a/drivers/net/e1000/e1000_ethtool.c
+++ b/drivers/net/e1000/e1000_ethtool.c
@@ -110,7 +110,7 @@
 	"Interrupt test (offline)", "Loopback test  (offline)",
 	"Link test   (on/offline)"
 };
-#define E1000_TEST_LEN sizeof(e1000_gstrings_test) / ETH_GSTRING_LEN
+#define E1000_TEST_LEN	ARRAY_SIZE(e1000_gstrings_test)
 
 static int
 e1000_get_settings(struct net_device *netdev, struct ethtool_cmd *ecmd)