mlx4_en: dont change mac_header on xmit

A driver xmit function is not allowed to change skb without special
care.

mlx4_en_xmit() should not call skb_reset_mac_header() and instead should
use skb->data to access ethernet header.

This removes a dumb test : if (ethh && ethh->h_dest)

Also remove this slow mlx4_en_mac_to_u64() call, we can use
get_unaligned() to get faster code.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Yevgeny Petrilin <yevgenyp@mellanox.co.il>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/mlx4/qp.h b/include/linux/mlx4/qp.h
index bee8fa2..091f9e7 100644
--- a/include/linux/mlx4/qp.h
+++ b/include/linux/mlx4/qp.h
@@ -212,7 +212,10 @@
 	 * [1]   SE (solicited event)
 	 * [0]   FL (force loopback)
 	 */
-	__be32			srcrb_flags;
+	union {
+		__be32			srcrb_flags;
+		__be16			srcrb_flags16[2];
+	};
 	/*
 	 * imm is immediate data for send/RDMA write w/ immediate;
 	 * also invalidation key for send with invalidate; input