drm/amdgpu: Use drm_dev_unplug in PCI .remove

This at least allows to fail any subsequent IOCTLs with -ENODEV
after the device is gone.
Still this operation is not supported yet in graphic mode
and will lead at least to page faults and other issues.

Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

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

@@ -978,8 +978,8 @@ amdgpu_pci_remove(struct pci_dev *pdev)
 {
 	struct drm_device *dev = pci_get_drvdata(pdev);
 
-	drm_dev_unregister(dev);
-	drm_dev_put(dev);
+	DRM_ERROR("Device removal is currently not supported outside of fbcon\n");
+	drm_dev_unplug(dev);
 	pci_disable_device(pdev);
 	pci_set_drvdata(pdev, NULL);
 }