net: ethernet: mtk-star-emac: fix wrong unmap in RX handling

mtk_star_dma_unmap_rx() should unmap the dma_addr of old skb rather than
that of new skb.
Assign new_dma_addr to desc_data.dma_addr after all handling of old skb
ends to avoid unexpected receive side error.

Fixes: f96e9641 ("net: ethernet: mtk-star-emac: fix error path in RX handling")
Signed-off-by: Biao Huang <biao.huang@mediatek.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/mediatek/mtk_star_emac.c

@@ -1225,8 +1225,6 @@ static int mtk_star_receive_packet(struct mtk_star_priv *priv)
 		goto push_new_skb;
 	}
 
-	desc_data.dma_addr = new_dma_addr;
-
 	/* We can't fail anymore at this point: it's safe to unmap the skb. */
 	mtk_star_dma_unmap_rx(priv, &desc_data);
 
@@ -1236,6 +1234,9 @@ static int mtk_star_receive_packet(struct mtk_star_priv *priv)
 	desc_data.skb->dev = ndev;
 	netif_receive_skb(desc_data.skb);
 
+	/* update dma_addr for new skb */
+	desc_data.dma_addr = new_dma_addr;
+
 push_new_skb:
 	desc_data.len = skb_tailroom(new_skb);
 	desc_data.skb = new_skb;