ARM: socfpga: Enable DM RTC bootcount on ABB SECU1

Add and enable RTC-backed boot counter on ABB SECU1 platform.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Ley Foon Tan <ley.foon.tan@intel.com>
Cc: Simon Goldschmidt <simon.k.r.goldschmidt@gmail.com>
Reviewed-by: Ley Foon Tan <ley.foon.tan@intel.com>