drm/amdgpu: Avoid leaking PM domain on driver unbind (v2)

We only support vga_switcheroo and runtime pm on PX/HG systems
so forcing runpm to 1 doesn't do anything useful anyway.

Only call vga_switcheroo_init_domain_pm_ops() for PX/HG so
that the cleanup path is correct as well.  This mirrors what
radeon does as well.

v2: rework the patch originally sent by Lukas (Alex)
Acked-by: Lukas Wunner <lukas@wunner.de>
Reported-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de> (v1)
Cc: stable@vger.kernel.org

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

@@ -1874,8 +1874,6 @@ int amdgpu_device_init(struct amdgpu_device *adev,
 	 * ignore it */
 	vga_client_register(adev->pdev, adev, NULL, amdgpu_device_vga_set_decode);
 
-	if (amdgpu_runtime_pm == 1)
-		runtime = true;
 	if (amdgpu_device_is_px(ddev))
 		runtime = true;
 	if (!pci_is_thunderbolt_attached(adev->pdev))