leds: lp55xx: add support for Device Tree bindings

This patch allows the lp5521 driver to be successfully probed and
initialised when Device Tree support is enabled.

Based on a patch by Gabriel Fernandez, rewritten in accordance
with review feedback.

Cc: Gabriel Fernandez <gabriel.fernandez@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Milo Kim <milo.kim@ti.com>
Signed-off-by: Bryan Wu <cooloney@gmail.com>
diff --git a/drivers/leds/leds-lp55xx-common.h b/drivers/leds/leds-lp55xx-common.h
index fa6a078..dbbf86d 100644
--- a/drivers/leds/leds-lp55xx-common.h
+++ b/drivers/leds/leds-lp55xx-common.h
@@ -135,4 +135,8 @@
 extern int lp55xx_register_sysfs(struct lp55xx_chip *chip);
 extern void lp55xx_unregister_sysfs(struct lp55xx_chip *chip);
 
+/* common device tree population function */
+extern int lp55xx_of_populate_pdata(struct device *dev,
+				    struct device_node *np);
+
 #endif /* _LEDS_LP55XX_COMMON_H */