ARM: ux500: Kconfig: Compile in leds-gpio support for Snowball

Code exists in the mop500 board file (used for HREF and Snowball)
to initialise Snowball's user LED via the leds-gpio driver. However,
the driver isn't currently built when using the current configuration.
This patch aims to change that behavior.
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Lee Jones <lee.jones@linaro.org>

arch/arm/mach-ux500/Kconfig

@@ -41,6 +41,7 @@ config MACH_HREFV60
 config MACH_SNOWBALL
 	bool "U8500 Snowball platform"
 	select MACH_MOP500
+	select LEDS_GPIO
 	help
 	  Include support for the snowball development platform.