dm: core: Alloc uclass-private data to be cache-aligned

There is no reason why this feature should not be supported for uclass-
private data. Update the code accordingly.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/include/dm/uclass.h b/include/dm/uclass.h
index 6e7c1cd..eebf2d5 100644
--- a/include/dm/uclass.h
+++ b/include/dm/uclass.h
@@ -44,6 +44,9 @@
 /* Members of this uclass sequence themselves with aliases */
 #define DM_UC_FLAG_SEQ_ALIAS			(1 << 0)
 
+/* Same as DM_FLAG_ALLOC_PRIV_DMA */
+#define DM_UC_FLAG_ALLOC_PRIV_DMA		(1 << 5)
+
 /**
  * struct uclass_driver - Driver for the uclass
  *