igc: Fix possible system crash when loading module

Guarantee that when probe() is run again, PTM and PCI busmaster will be
in the same state as it was if the driver was never loaded.

Avoid an i225/i226 hardware issue that PTM requests can be made even
though PCI bus mastering is not enabled. These unexpected PTM requests
can crash some systems.

So, "force" disable PTM and busmastering before removing the driver,
so they can be re-enabled in the right order during probe(). This is
more like a workaround and should be applicable for i225 and i226, in
any platform.

Fixes: 1b5d73fb86 ("igc: Enable PCIe PTM")
Signed-off-by: Vinicius Costa Gomes <vinicius.gomes@intel.com>
Reviewed-by: Muhammad Husaini Zulkifli <muhammad.husaini.zulkifli@intel.com>
Tested-by: Naama Meir <naamax.meir@linux.intel.com>
Signed-off-by: Tony Nguyen <anthony.l.nguyen@intel.com>

drivers/net/ethernet/intel/igc/igc_main.c

@@ -6730,6 +6730,9 @@ static void igc_remove(struct pci_dev *pdev)
 
 	igc_ptp_stop(adapter);
 
+	pci_disable_ptm(pdev);
+	pci_clear_master(pdev);
+
 	set_bit(__IGC_DOWN, &adapter->state);
 
 	del_timer_sync(&adapter->watchdog_timer);