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: NShawn Guo <shawn.guo@freescale.com>
Signed-off-by: NSascha Hauer <s.hauer@pengutronix.de>

arch/arm/configs/mx51_defconfig

@@ -110,7 +110,7 @@ CONFIG_MMC=y
 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