ddr: socfpga: Enable ARM64 Non-Secure SDRAM ECC Access

The ECC registers in the SDRAM HMC Adapter should always
be accessible (both when ECC is enabled and disabled).
Currently, the registers are accessible only when ECC is enabled.

The ECC Enabled bit is used to determine the status of
ECC by later OSes so always allow access.

Signed-off-by: Thor Thayer <thor.thayer@linux.intel.com>
Reviewed-by: Ley Foon Tan <ley.foon.tan@intel.com>