i40evf: fix panic during MTU change

Down was requesting queue disables, but then exited immediately
without waiting for the queues to actually disable.  This could
allow any function called after i40evf_down to run immediately,
including i40evf_up, and causes a memory leak.

Removing the whole reinit_locked function is the best way
to go about this, and allows for the driver to handle the
state changes by requesting reset from the periodic timer.

Also, add a couple WARN_ONs in slow path to help us recognize
if we re-introduce this issue or missed any cases.

Signed-off-by: Mitch Williams <mitch.a.williams@intel.com>
Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
diff --git a/drivers/net/ethernet/intel/i40evf/i40evf_ethtool.c b/drivers/net/ethernet/intel/i40evf/i40evf_ethtool.c
index f4e7766..2b53c87 100644
--- a/drivers/net/ethernet/intel/i40evf/i40evf_ethtool.c
+++ b/drivers/net/ethernet/intel/i40evf/i40evf_ethtool.c
@@ -267,8 +267,10 @@
 	adapter->tx_desc_count = new_tx_count;
 	adapter->rx_desc_count = new_rx_count;
 
-	if (netif_running(netdev))
-		i40evf_reinit_locked(adapter);
+	if (netif_running(netdev)) {
+		adapter->flags |= I40EVF_FLAG_RESET_NEEDED;
+		schedule_work(&adapter->reset_task);
+	}
 
 	return 0;
 }