arm/zynq: Add software system reset via SCLR Support software-driven system reset via the register in the SCLR. Signed-off-by: Sebastian Huber <sebastian.huber@embedded-brains.de> Reviewed-by: Peter Crosthwaite <peter.crosthwaite@xilinx.com> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>