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>