drm/msm/gpu: use pm-runtime

We need to use pm-runtime properly when IOMMU is using device_link() to
control it's own clocks.

Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_drv.c

@@ -265,6 +265,8 @@ static int msm_drm_uninit(struct device *dev)
 
 	if (gpu) {
 		mutex_lock(&ddev->struct_mutex);
+		// XXX what do we do here?
+		//pm_runtime_enable(&pdev->dev);
 		gpu->funcs->pm_suspend(gpu);
 		mutex_unlock(&ddev->struct_mutex);
 		gpu->funcs->destroy(gpu);