dm: core: Add a function to get a uclass name

It is useful in debug() statements to display the name of the uclass for a
device. Add a simple function to provide this.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>

include/dm/uclass.h

@@ -118,6 +118,14 @@ struct uclass_driver {
  */
 int uclass_get(enum uclass_id key, struct uclass **ucp);
 
+/**
+ * uclass_get_name() - Get the name of a uclass driver
+ *
+ * @id: ID to look up
+ * @returns the name of the uclass driver for that ID, or NULL if none
+ */
+const char *uclass_get_name(enum uclass_id id);
+
 /**
  * uclass_get_device() - Get a uclass device based on an ID and index
  *