leds: Fix build for LEDS_CLASS=m on versatile

I got a build error today, since LEDS_VERSATILE can be built-in while LEDS_CLASS
is a module:

drivers/built-in.o: In function `versatile_leds_probe':
:(.text+0x155020): undefined reference to `led_classdev_register'

I suggest we turn this option into 'tristate' so that the dependency
tracking works correctly.
Signed-off-by: NArnd Bergmann <arnd@arndb.de>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Signed-off-by: NOlof Johansson <olof@lixom.net>

drivers/leds/Kconfig

@@ -488,7 +488,7 @@ config LEDS_BLINKM
 	  through I2C. Say Y to enable support for the BlinkM LED.
 
 config LEDS_VERSATILE
-	bool "LED support for the ARM Versatile and RealView"
+	tristate "LED support for the ARM Versatile and RealView"
 	depends on ARCH_REALVIEW || ARCH_VERSATILE
 	depends on LEDS_CLASS
 	help