net: rswitch: Fix return value in rswitch_start_xmit()

This .ndo_start_xmit() function should return netdev_tx_t value,
not -ENOMEM. So, fix it.

Fixes: 33f5d733 ("net: renesas: rswitch: Improve TX timestamp accuracy")
Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/renesas/rswitch.c

@@ -1535,7 +1535,7 @@ static netdev_tx_t rswitch_start_xmit(struct sk_buff *skb, struct net_device *nd
 		ts_info = kzalloc(sizeof(*ts_info), GFP_ATOMIC);
 		if (!ts_info) {
 			dma_unmap_single(ndev->dev.parent, dma_addr, skb->len, DMA_TO_DEVICE);
-			return -ENOMEM;
+			return ret;
 		}
 
 		skb_shinfo(skb)->tx_flags |= SKBTX_IN_PROGRESS;