drm/i915: checking for NULL instead of IS_ERR()

i915_gem_vma_create() returns and ERR_PTR() or a valid pointer, it never
returns NULL.
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/i915/i915_gem.c

@@ -3134,9 +3134,9 @@ i915_gem_object_bind_to_gtt(struct drm_i915_gem_object *obj,
 	i915_gem_object_pin_pages(obj);
 
 	vma = i915_gem_vma_create(obj, &dev_priv->gtt.base);
-	if (vma == NULL) {
+	if (IS_ERR(vma)) {
 		i915_gem_object_unpin_pages(obj);
-		return -ENOMEM;
+		return PTR_ERR(vma);
 	}
 
 search_free:

drivers/gpu/drm/i915/i915_gem_stolen.c

@@ -392,8 +392,8 @@ i915_gem_object_create_stolen_for_preallocated(struct drm_device *dev,
 		return obj;
 
 	vma = i915_gem_vma_create(obj, &dev_priv->gtt.base);
-	if (!vma) {
-		ret = -ENOMEM;
+	if (IS_ERR(vma)) {
+		ret = PTR_ERR(vma);
 		goto err_out;
 	}