drm/amdgpu: Verify DMA opearations from device are done

In case device remove is just simualted by sysfs then verify
device doesn't keep doing DMA to the released memory after
pci_remove is done.
Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Acked-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210512142648.666476-16-andrey.grodzovsky@amd.com

drivers/gpu/drm/amd/amdgpu/amdgpu_drv.c

@@ -1314,7 +1314,13 @@ amdgpu_pci_remove(struct pci_dev *pdev)
 	drm_dev_unplug(dev);
 	amdgpu_driver_unload_kms(dev);
 
+	/*
+	 * Flush any in flight DMA operations from device.
+	 * Clear the Bus Master Enable bit and then wait on the PCIe Device
+	 * StatusTransactions Pending bit.
+	 */
 	pci_disable_device(pdev);
+	pci_wait_for_pending_transaction(pdev);
 }
 
 static void