i40e: Remove rx page reuse double count

Page reuse was being tracked from two locations:
  - i40e_reuse_rx_page (via 40e_clean_rx_irq), and
  - i40e_alloc_mapped_page

Remove the double count and only count reuse from i40e_alloc_mapped_page
when the page is about to be reused.
Signed-off-by: Joe Damato <jdamato@fastly.com>
Tested-by: Dave Switzer <david.switzer@intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/i40e/i40e_txrx.c

@@ -1382,8 +1382,6 @@ static void i40e_reuse_rx_page(struct i40e_ring *rx_ring,
 	new_buff->page_offset	= old_buff->page_offset;
 	new_buff->pagecnt_bias	= old_buff->pagecnt_bias;
 
-	rx_ring->rx_stats.page_reuse_count++;
-
 	/* clear contents of buffer_info */
 	old_buff->page = NULL;
 }