Otherwise, I got below build error when CONFIG_LEDS_CLASS=m.

  LD      init/built-in.o
drivers/built-in.o: In function `asic3_led_probe':
clkdev.c:(.devinit.text+0x4680): undefined reference to `led_classdev_register'
drivers/built-in.o: In function `r_tpu_probe':
clkdev.c:(.devinit.text+0x4838): undefined reference to `led_classdev_register'
drivers/built-in.o: In function `asic3_led_remove':
clkdev.c:(.devexit.text+0x564): undefined reference to `led_classdev_unregister'
drivers/built-in.o: In function `r_tpu_remove':
clkdev.c:(.devexit.text+0x5a0): undefined reference to `led_classdev_unregister'
make: *** [vmlinux] Error 1
Signed-off-by: Axel Lin <axel.lin@gmail.com>
Signed-off-by: Bryan Wu <bryan.wu@canonical.com>