ksz884x: fix mtu for VLAN

The Ethernet header does not account for the addition of a VLAN header.
Full size Ethernet frames containing VLAN header are not processed
because the frame is larger than the resulting hw mtu.
Signed-off-by: Doug Kehn <rdkehn@yahoo.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/micrel/ksz884x.c

@@ -746,7 +746,7 @@
 #define MAC_ADDR_ORDER(i)		(ETH_ALEN - 1 - (i))
 
 #define MAX_ETHERNET_BODY_SIZE		1500
-#define ETHERNET_HEADER_SIZE		14
+#define ETHERNET_HEADER_SIZE		(14 + VLAN_HLEN)
 
 #define MAX_ETHERNET_PACKET_SIZE	\
 	(MAX_ETHERNET_BODY_SIZE + ETHERNET_HEADER_SIZE)