net: hns: avoid uninitialized variable warning:

gcc fails to see that the use of the 'last_offset' variable
in hns_nic_reuse_page() is used correctly and issues a bogus
warning:

drivers/net/ethernet/hisilicon/hns/hns_enet.c: In function 'hns_nic_reuse_page':
drivers/net/ethernet/hisilicon/hns/hns_enet.c:541:6: warning: 'last_offset' may be used uninitialized in this function [-Wmaybe-uninitialized]

This simplifies the function to make it more obvious what is
going on to both readers and compilers, which makes the warning
go away.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns/hns_enet.c

@@ -499,30 +499,28 @@ static void hns_nic_reuse_page(struct sk_buff *skb, int i,
 	struct hnae_desc *desc;
 	int truesize, size;
 	int last_offset;
+	bool twobufs;
+
+	twobufs = ((PAGE_SIZE < 8192) && hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048);
 
 	desc = &ring->desc[ring->next_to_clean];
 	size = le16_to_cpu(desc->rx.size);
 
-#if (PAGE_SIZE < 8192)
-	if (hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048) {
+	if (twobufs) {
 		truesize = hnae_buf_size(ring);
 	} else {
 		truesize = ALIGN(size, L1_CACHE_BYTES);
 		last_offset = hnae_page_size(ring) - hnae_buf_size(ring);
 	}
 
-#else
-	truesize = ALIGN(size, L1_CACHE_BYTES);
-	last_offset = hnae_page_size(ring) - hnae_buf_size(ring);
-#endif
-
 	skb_add_rx_frag(skb, i, desc_cb->priv, desc_cb->page_offset + pull_len,
 			size - pull_len, truesize - pull_len);
 
 	 /* avoid re-using remote pages,flag default unreuse */
-	if (likely(page_to_nid(desc_cb->priv) == numa_node_id())) {
-#if (PAGE_SIZE < 8192)
-		if (hnae_buf_size(ring) == HNS_BUFFER_SIZE_2048) {
+	if (unlikely(page_to_nid(desc_cb->priv) != numa_node_id()))
+		return;
+
+	if (twobufs) {
 		/* if we are only owner of page we can reuse it */
 		if (likely(page_count(desc_cb->priv) == 1)) {
 			/* flip page offset to other buffer */
@@ -534,7 +532,7 @@ static void hns_nic_reuse_page(struct sk_buff *skb, int i,
 		}
 		return;
 	}
-#endif
+
 	/* move offset up to the next cache line */
 	desc_cb->page_offset += truesize;
 
@@ -543,7 +541,6 @@ static void hns_nic_reuse_page(struct sk_buff *skb, int i,
 		/* bump ref count on page before it is given*/
 		get_page(desc_cb->priv);
 	}
-	}
 }
 
 static void get_v2rx_desc_bnum(u32 bnum_flag, int *out_bnum)