igb: call igb_ptp_suspend during suspend/resume cycle

Properly stop the extra workqueue items and ensure that we resume
cleanly. This is better than using igb_ptp_init and igb_ptp_stop since
these functions destroy the PHC device, which will cause other problems
if we do so. Since igb_ptp_reset now re-schedules the work-queue item we
don't need an equivalent igb_ptp_resume in the resume workflow.
Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Tested-by: Aaron Brown <aaron.f.brown@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>

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

@@ -7528,6 +7528,8 @@ static int __igb_shutdown(struct pci_dev *pdev, bool *enable_wake,
 	if (netif_running(netdev))
 		__igb_close(netdev, true);
 
+	igb_ptp_suspend(adapter);
+
 	igb_clear_interrupt_scheme(adapter);
 
 #ifdef CONFIG_PM