ravb: remove tx buffer addr 4byte alilgnment restriction for R-Car Gen3

This patch sets from two descriptor to one descriptor because R-Car Gen3
does not have the 4 bytes alignment restriction of the transmission buffer.

Signed-off-by: Kazuya Mizuguchi <kazuya.mizuguchi.ks@renesas.com>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/drivers/net/ethernet/renesas/ravb.h b/drivers/net/ethernet/renesas/ravb.h
index 1470fc1..b2b1803 100644
--- a/drivers/net/ethernet/renesas/ravb.h
+++ b/drivers/net/ethernet/renesas/ravb.h
@@ -954,7 +954,10 @@
 #define RX_QUEUE_OFFSET	4
 #define NUM_RX_QUEUE	2
 #define NUM_TX_QUEUE	2
-#define NUM_TX_DESC	2	/* TX descriptors per packet */
+
+/* TX descriptors per packet */
+#define NUM_TX_DESC_GEN2	2
+#define NUM_TX_DESC_GEN3	1
 
 struct ravb_tstamp_skb {
 	struct list_head list;
@@ -1033,6 +1036,7 @@
 	unsigned no_avb_link:1;
 	unsigned avb_link_active_low:1;
 	unsigned wol_enabled:1;
+	int num_tx_desc;	/* TX descriptors per packet */
 };
 
 static inline u32 ravb_read(struct net_device *ndev, enum ravb_reg reg)