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>

drivers/net/cassini.c

@@ -4394,7 +4394,7 @@ static struct {
 	{"tx_fifo_errors"},
 	{"tx_packets"}
 };
-#define CAS_NUM_STAT_KEYS (sizeof(ethtool_cassini_statnames)/ETH_GSTRING_LEN)
+#define CAS_NUM_STAT_KEYS ARRAY_SIZE(ethtool_cassini_statnames)
 
 static struct {
 	const int offsets;	/* neg. values for 2nd arg to cas_read_phy */