drm/msm: Fix dereference of pointer minor before null check

Currently the pointer minor is being dereferenced before it is null
checked, leading to a potential null pointer dereference issue. Fix this
by dereferencing the pointer only after it has been null checked. Also
Replace minor->dev with dev.

Fixes: 4f89cf40d01e ("drm/msm: bail out late_init_minor() if it is not a GPU device")
Signed-off-by: Colin Ian King <[e-mail]>
Reviewed-by: Konrad Dybcio <[e-mail]>
Patchwork: https://patchwork.freedesktop.org/patch/666259/
Signed-off-by: Rob Clark <[e-mail]>

drivers/gpu/drm/msm/msm_debugfs.c

···
 
 static int late_init_minor(struct drm_minor *minor)
 {
-	struct drm_device *dev = minor->dev;
-	struct msm_drm_private *priv = dev->dev_private;
+	struct drm_device *dev;
+	struct msm_drm_private *priv;
 	int ret;
 
 	if (!minor)
 		return 0;
+
+	dev = minor->dev;
+	priv = dev->dev_private;
 
 	if (!priv->gpu_pdev)
 		return 0;
 
 	ret = msm_rd_debugfs_init(minor);
 	if (ret) {
-		DRM_DEV_ERROR(minor->dev->dev, "could not install rd debugfs\n");
+		DRM_DEV_ERROR(dev->dev, "could not install rd debugfs\n");
 		return ret;
 	}
 
 	ret = msm_perf_debugfs_init(minor);
 	if (ret) {
-		DRM_DEV_ERROR(minor->dev->dev, "could not install perf debugfs\n");
+		DRM_DEV_ERROR(dev->dev, "could not install perf debugfs\n");
 		return ret;
 	}