mlx4: use netdev_rss_key_fill() helper

Use of well known RSS key increases attack surface.
Switch to a random one, using generic helper so that all
ports share a common key.

Also provide ethtool -x support to fetch RSS key

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Amir Vadai <amirv@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/mlx4/qp.h b/include/linux/mlx4/qp.h
index 5f4e36c..467ccdf 100644
--- a/include/linux/mlx4/qp.h
+++ b/include/linux/mlx4/qp.h
@@ -120,13 +120,15 @@
 	MLX4_RSS_QPC_FLAG_OFFSET		= 13,
 };
 
+#define MLX4_EN_RSS_KEY_SIZE 40
+
 struct mlx4_rss_context {
 	__be32			base_qpn;
 	__be32			default_qpn;
 	u16			reserved;
 	u8			hash_fn;
 	u8			flags;
-	__be32			rss_key[10];
+	__be32			rss_key[MLX4_EN_RSS_KEY_SIZE / sizeof(__be32)];
 	__be32			base_qpn_udp;
 };