ARM: mx51_defconfig: change CONFIG_LEDS_CLASS 'm' to 'y'

This patch is to fix the warning below.

arch/arm/configs/mx51_defconfig:113:warning: symbol value 'm' invalid for LEDS_CLASS

Signed-off-by: Shawn Guo <shawn.guo@freescale.com>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
diff --git a/arch/arm/configs/mx51_defconfig b/arch/arm/configs/mx51_defconfig
index 9cba68c..e3c9032 100644
--- a/arch/arm/configs/mx51_defconfig
+++ b/arch/arm/configs/mx51_defconfig
@@ -110,7 +110,7 @@
 CONFIG_MMC_BLOCK=m
 CONFIG_MMC_SDHCI=m
 CONFIG_NEW_LEDS=y
-CONFIG_LEDS_CLASS=m
+CONFIG_LEDS_CLASS=y
 CONFIG_RTC_CLASS=y
 CONFIG_RTC_INTF_DEV_UIE_EMUL=y
 CONFIG_EXT2_FS=y