drm/ttm: Delete an unnecessary check before the function call “ttm_tt_destroy”

Author: Markus Elfring <elfring@users.sourceforge.net>

The ttm_tt_destroy() 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 
Signed-off-by: Daniel Vetter 
Link: http://patchwork.freedesktop.org/patch/msgid/54338f58-830c-a8b4-4554-5d4459bcd321@users.sourceforge.net
 drivers/gpu/drm/ttm/ttm_bo.c | 4 +---
 1 file changed, 1 insertion(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/ttm/ttm_bo.c b/drivers/gpu/drm/ttm/ttm_bo.c
index 39386f5..4e55863 100644
--- a/drivers/gpu/drm/ttm/ttm_bo.c
+++ b/drivers/gpu/drm/ttm/ttm_bo.c
@@ -146,9 +146,7 @@ static void ttm_bo_release_list(struct kref *list_kref)
 	BUG_ON(bo->mem.mm_node != NULL);
-	if (bo->ttm)
-		ttm_tt_destroy(bo->ttm);
+	ttm_tt_destroy(bo->ttm);
 	if (bo->resv == &bo->ttm_resv)