dm: core: Add a function to look up a uclass by name

Each uclass has a driver name which we can use to look up the uclass. This
is useful for logging, where the uclass ID is used as the category.

Add a function to handle this, as well as a test.

Signed-off-by: Simon Glass <sjg@chromium.org>

include/dm/uclass.h

@@ -127,6 +127,14 @@ int uclass_get(enum uclass_id key, struct uclass **ucp);
  */
 const char *uclass_get_name(enum uclass_id id);
 
+/**
+ * uclass_get_by_name() - Look up a uclass by its driver name
+ *
+ * @name: Name to look up
+ * @returns the associated uclass ID, or UCLASS_INVALID if not found
+ */
+enum uclass_id uclass_get_by_name(const char *name);
+
 /**
  * uclass_get_device() - Get a uclass device based on an ID and index
  *