led-class: change back LEDS_CLASS to tristate instead of bool

After moving some core functions to led-core.c, led-class.c can be built
as module again.

Signed-off-by: Bryan Wu <bryan.wu@canonical.com>
Acked-by: Richard Purdie <richard.purdie@linuxfoundation.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/drivers/leds/Kconfig b/drivers/leds/Kconfig
index e2ac190..589ba02 100644
--- a/drivers/leds/Kconfig
+++ b/drivers/leds/Kconfig
@@ -17,7 +17,7 @@
 if NEW_LEDS
 
 config LEDS_CLASS
-	bool "LED Class Support"
+	tristate "LED Class Support"
 	help
 	  This option enables the led sysfs class in /sys/class/leds.  You'll
 	  need this to do anything useful with LEDs.  If unsure, say N.