arm64: zynqmp: Enable reset and poweroff via sysreset framework

reset and poweroff are called via hooks in psci driver which is going
around sysreset framework that's why enable sysreset drivers and do reset
and poweroff via this framework. Using this flow will allow us to call
SYSTEM_WARM_RESET based on psci 1.1 spec which can be calles with reset -w
command.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>