arcnet: cleanup sizeof parameter

This patch doesn't change the compiled code because ARC_HDR_SIZE is 4
and sizeof(int) is 4, but the intent was to use the header size and not
the sizeof the header size.
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/arcnet/arcnet.c

@@ -1007,7 +1007,7 @@ static void arcnet_rx(struct net_device *dev, int bufnum)
 
 	soft = &pkt.soft.rfc1201;
 
-	lp->hw.copy_from_card(dev, bufnum, 0, &pkt, sizeof(ARC_HDR_SIZE));
+	lp->hw.copy_from_card(dev, bufnum, 0, &pkt, ARC_HDR_SIZE);
 	if (pkt.hard.offset[0]) {
 		ofs = pkt.hard.offset[0];
 		length = 256 - ofs;