arm: socfpga: soc64: Disable CONFIG_PSCI_RESET

Don't invoke 'SYSTEM_RESET' PSCI function because PSCI
function calls are not supported by u-boot running in EL3.

Signed-off-by: Chee Hong Ang <chee.hong.ang@intel.com>
Reviewed-by: Ley Foon Tan <ley.foon.tan@intel.com>