drm/ttm: move default BO destructor into VMWGFX v2

It's the only driver using this.

v2: use BUG_ON() in vmw_bo_create() as suggested by Zack
Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20220329110243.6335-5-christian.koenig@amd.com

drivers/gpu/drm/ttm/ttm_bo.c

@@ -44,12 +44,6 @@
 
 #include "ttm_module.h"
 
-/* default destructor */
-static void ttm_bo_default_destroy(struct ttm_buffer_object *bo)
-{
-	kfree(bo);
-}
-
 static void ttm_bo_mem_space_debug(struct ttm_buffer_object *bo,
 					struct ttm_placement *placement)
 {
@@ -936,8 +930,7 @@ int ttm_bo_init_reserved(struct ttm_device *bdev,
 	bool locked;
 	int ret;
 
-	bo->destroy = destroy ? destroy : ttm_bo_default_destroy;
-
+	bo->destroy = destroy;
 	kref_init(&bo->kref);
 	INIT_LIST_HEAD(&bo->ddestroy);
 	bo->bdev = bdev;

drivers/gpu/drm/vmwgfx/vmwgfx_bo.c

@@ -393,6 +393,12 @@ void vmw_bo_bo_free(struct ttm_buffer_object *bo)
 	kfree(vmw_bo);
 }
 
+/* default destructor */
+static void vmw_bo_default_destroy(struct ttm_buffer_object *bo)
+{
+	kfree(bo);
+}
+
 /**
  * vmw_bo_create_kernel - Create a pinned BO for internal kernel use.
  *
@@ -425,7 +431,7 @@ int vmw_bo_create_kernel(struct vmw_private *dev_priv, unsigned long size,
 
 	ret = ttm_bo_init_reserved(&dev_priv->bdev, bo, size,
 				   ttm_bo_type_kernel, placement, 0,
-				   &ctx, NULL, NULL, NULL);
+				   &ctx, NULL, NULL, vmw_bo_default_destroy);
 	if (unlikely(ret))
 		goto error_free;
 
@@ -448,6 +454,8 @@ int vmw_bo_create(struct vmw_private *vmw,
 {
 	int ret;
 
+	BUG_ON(!bo_free);
+
 	*p_bo = kmalloc(sizeof(**p_bo), GFP_KERNEL);
 	if (unlikely(!*p_bo)) {
 		DRM_ERROR("Failed to allocate a buffer.\n");