igb: fix stats for i210 rx_fifo_errors

commit e66c083a upstream.

RQDPC on i210/i211 is R/W not ReadClear. Clear after reading.
Signed-off-by: Todd Fujinaka <todd.fujinaka@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Cc: Tim Gardner <tim.gardner@canonical.com>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>

drivers/net/ethernet/intel/igb/igb_main.c

@@ -4909,8 +4909,10 @@ void igb_update_stats(struct igb_adapter *adapter,
 
 	rcu_read_lock();
 	for (i = 0; i < adapter->num_rx_queues; i++) {
-		u32 rqdpc = rd32(E1000_RQDPC(i));
 		struct igb_ring *ring = adapter->rx_ring[i];
+		u32 rqdpc = rd32(E1000_RQDPC(i));
+		if (hw->mac.type >= e1000_i210)
+			wr32(E1000_RQDPC(i), 0);
 
 		if (rqdpc) {
 			ring->rx_stats.drops += rqdpc;