leds-lp55xx: add new lp55xx_register_sysfs() for the firmware interface

 LP55xx family chips have internal program memory which run various patterns.
 Using this memory, LEDs continue on blinking/dimming without continuous I2C
 commands. That means the I2C HOST can be entered into sleep once the memory
 is updated.

 An application can get hex data from a file and write them into
 the program memory through the I2C. This is general firwmare interface.

 This patch is the initial step for adding the firmware interface.

Signed-off-by: Milo(Woogyom) 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 32d9682..d0be837 100644
--- a/drivers/leds/leds-lp55xx-common.h
+++ b/drivers/leds/leds-lp55xx-common.h
@@ -103,4 +103,8 @@
 				struct lp55xx_chip *chip);
 extern void lp55xx_unregister_leds(struct lp55xx_led *led,
 				struct lp55xx_chip *chip);
+
+/* common device attributes functions */
+extern int lp55xx_register_sysfs(struct lp55xx_chip *chip);
+
 #endif /* _LEDS_LP55XX_COMMON_H */