ARM: imx_v6_v7_defconfig: Enable RTC PCF8523 support

RTC PCF8523 is used on some mx6 cubox-i boards.

Let it work by default.
Reported-by: NRick Thomas <rbthomas@cube.rcthomas.org>
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NShawn Guo <shawn.guo@linaro.org>

arch/arm/configs/imx_v6_v7_defconfig

@@ -283,6 +283,7 @@ CONFIG_RTC_CLASS=y
 CONFIG_RTC_INTF_DEV_UIE_EMUL=y
 CONFIG_RTC_DRV_DS1307=y
 CONFIG_RTC_DRV_ISL1208=y
+CONFIG_RTC_DRV_PCF8523=y
 CONFIG_RTC_DRV_PCF8563=y
 CONFIG_RTC_DRV_MC13XXX=y
 CONFIG_RTC_DRV_MXC=y