igb: double increment nr_frags

There is no need to increment nr_frags because skb_fill_page_desc increments
it.
Signed-off-by: Koki Sanagi <sanagi.koki@jp.fujitsu.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/igb/igb_main.c

@@ -5248,7 +5248,7 @@ static bool igb_clean_rx_irq_adv(struct igb_q_vector *q_vector,
 				       PAGE_SIZE / 2, PCI_DMA_FROMDEVICE);
 			buffer_info->page_dma = 0;
 
-			skb_fill_page_desc(skb, skb_shinfo(skb)->nr_frags++,
+			skb_fill_page_desc(skb, skb_shinfo(skb)->nr_frags,
 						buffer_info->page,
 						buffer_info->page_offset,
 						length);