ixgbe: need not repeat init skb with NULL

Signed-off-by: Martin Zhang <martinbj2008@gmail.com>
Tested-by: Phil Schmitt <phillip.j.schmitt@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -4321,8 +4321,8 @@ static void ixgbe_clean_rx_ring(struct ixgbe_ring *rx_ring)
 				IXGBE_CB(skb)->page_released = false;
 			}
 			dev_kfree_skb(skb);
+			rx_buffer->skb = NULL;
 		}
-		rx_buffer->skb = NULL;
 		if (rx_buffer->dma)
 			dma_unmap_page(dev, rx_buffer->dma,
 				       ixgbe_rx_pg_size(rx_ring),