of: Add empty for_each_available_child_of_node() macro definition

Add this empty macro definition so users can be compiled without
excluding this macro call with preprocessor directives when CONFIG_OF
is disabled.
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Rob Herring <rob.herring@calxeda.com>

include/linux/of.h

@@ -366,6 +366,9 @@ static inline bool of_have_populated_dt(void)
 #define for_each_child_of_node(parent, child) \
 	while (0)
 
+#define for_each_available_child_of_node(parent, child) \
+	while (0)
+
 static inline struct device_node *of_get_child_by_name(
 					const struct device_node *node,
 					const char *name)