drm/msm: correct attempted NULL pointer dereference in put_iova

put_iova() would attempt to dereference a NULL pointer via the
address space pointer when no IOMMU is present. Correct this by adding
the appropriate check.
Signed-off-by: Brian Masney <masneyb@onstation.org>
Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/msm_gem.c

@@ -352,8 +352,10 @@ put_iova(struct drm_gem_object *obj)
 	WARN_ON(!mutex_is_locked(&msm_obj->lock));
 
 	list_for_each_entry_safe(vma, tmp, &msm_obj->vmas, list) {
-		msm_gem_purge_vma(vma->aspace, vma);
-		msm_gem_close_vma(vma->aspace, vma);
+		if (vma->aspace) {
+			msm_gem_purge_vma(vma->aspace, vma);
+			msm_gem_close_vma(vma->aspace, vma);
+		}
 		del_vma(vma);
 	}
 }