leds: Add no-op gpio_led_register_device when LED subsystem is disabled

Some systems use 'gpio_led_register_device' to make an in-memory copy of
their LED device table so the original can be removed as .init.rodata.
When the LED subsystem is not enabled source in the led directory is not
built and so this function may be undefined. Fix this here.
Signed-off-by: Andrew F. Davis <afd@ti.com>
Signed-off-by: Jacek Anaszewski <j.anaszewski@samsung.com>

include/linux/leds.h

@@ -387,8 +387,16 @@ struct gpio_led_platform_data {
 					unsigned long *delay_off);
 };
 
+#ifdef CONFIG_NEW_LEDS
 struct platform_device *gpio_led_register_device(
 		int id, const struct gpio_led_platform_data *pdata);
+#else
+static inline struct platform_device *gpio_led_register_device(
+		int id, const struct gpio_led_platform_data *pdata)
+{
+	return 0;
+}
+#endif
 
 enum cpu_led_event {
 	CPU_LED_IDLE_START,	/* CPU enters idle */