net: ethernet: bgmac: use #defines for MAX size

The maximum frame size is really just the standard ethernet frame size
and FCS.  So use those existing defines to make the code a little more
beautiful.
Signed-off-by: Jon Mason <jon.mason@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/broadcom/bgmac.h

@@ -402,7 +402,7 @@
 
 #define BGMAC_WEIGHT	64
 
-#define ETHER_MAX_LEN   1518
+#define ETHER_MAX_LEN	(ETH_FRAME_LEN + ETH_FCS_LEN)
 
 /* Feature Flags */
 #define BGMAC_FEAT_TX_MASK_SETUP	BIT(0)