dt: add empty for_each_child_of_node, of_find_property

The patch adds a couple empty functions for non-dt build, so that
drivers migrating to dt can save some '#ifdef CONFIG_OF'.
Signed-off-by: NStephen Warren <swarren@nvidia.com>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

include/linux/of.h

@@ -249,6 +249,16 @@ static inline bool of_have_populated_dt(void)
 	return false;
 }
 
+#define for_each_child_of_node(parent, child) \
+	while (0)
+
+static inline struct property *of_find_property(const struct device_node *np,
+						const char *name,
+						int *lenp)
+{
+	return NULL;
+}
+
 static inline int of_property_read_u32_array(const struct device_node *np,
 					     const char *propname,
 					     u32 *out_values, size_t sz)