cleanup: add a scoped version of CLASS()

This will make it possible to use:

scoped_class() {
}

constructs to limit variables to certain scopes and still perform
auto-cleanup.

Signed-off-by: Christian Brauner <brauner@kernel.org>

include/linux/cleanup.h

@@ -277,6 +277,14 @@ static inline class_##_name##_t class_##_name##ext##_constructor(_init_args) \
 	class_##_name##_t var __cleanup(class_##_name##_destructor) =	\
 		class_##_name##_constructor
 
+#define scoped_class(_name, var, args)                          \
+	for (CLASS(_name, var)(args);                           \
+	     __guard_ptr(_name)(&var) || !__is_cond_ptr(_name); \
+	     ({ goto _label; }))                                \
+		if (0) {                                        \
+_label:                                                         \
+			break;                                  \
+		} else
 
 /*
  * DEFINE_GUARD(name, type, lock, unlock):