bmips: switch to napi_build_skb() to reuse skbuff_heads

napi_build_skb() reuses NAPI skbuff_head cache in order to save some
cycles on freeing/allocating skbuff_heads on every new rx or completed
tx.
Use napi_consume_skb() to feed the cache with skbuff_heads of completed
tx so it's never empty.

Signed-off-by: Sieng Piaw Liew <[email protected]>

target/linux/bmips/files/drivers/net/ethernet/broadcom/bcm6368-enetsw.c

@@ -407,7 +407,7 @@ static int bcm6368_enetsw_receive_queue(struct net_device *dev, int budget)
 			frag_size = priv->rx_frag_size;
 		}
 
-		skb = build_skb(buf, frag_size);
+		skb = napi_build_skb(buf, frag_size);
 		if (unlikely(!skb)) {
 			skb_free_frag(buf);
 			dev->stats.rx_dropped++;
@@ -475,7 +475,7 @@ static int bcm6368_enetsw_tx_reclaim(struct net_device *dev, int force)
 		if (desc->len_stat & DMADESC_UNDER_MASK)
 			dev->stats.tx_errors++;
 
-		dev_kfree_skb(skb);
+		napi_consume_skb(skb, !force);
 		released++;
 	}