From: Tony Lindgren <tony@atomide.com>
Date: Mon, 27 Oct 2014 13:25:56 -0700

+/**
+ * of_try_set_control_gpio - configure a gpio if it exists
+ */
+static int try_toggle_control_gpio(struct device *dev,
+				   struct gpio_desc **desc,
+				   const char *name, int index,
+				   int value, unsigned int nsdelay)

This needs to be under CONFIG_OF cpp protection just like the code that
calls it.