rtc: ep93xx: Use readl/writel for io

Drivers should not be using the __raw_* io accessors.

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Alessandro Zummo <a.zummo@towertech.it>
Signed-off-by: Alexandre Belloni <alexandre.belloni@free-electrons.com>