drm/msm: Delete an unnecessary check before drm_gem_object_unreference()

The drm_gem_object_unreference() function tests whether its argument
is NULL and then returns immediately.
Thus the test around the call is not needed.

This issue was detected by using the Coccinelle software.
Signed-off-by: Markus Elfring <elfring@users.sourceforge.net>
Signed-off-by: Rob Clark <robdclark@gmail.com>

drivers/gpu/drm/msm/msm_gem.c

@@ -830,9 +830,7 @@ struct drm_gem_object *msm_gem_new(struct drm_device *dev,
 	return obj;
 
 fail:
-	if (obj)
-		drm_gem_object_unreference(obj);
-
+	drm_gem_object_unreference(obj);
 	return ERR_PTR(ret);
 }