ARM: dts: vf610: add system reset controller and syscon-reboot

Add the system reset controller (SRC) module and use syscon-reboot
to register a restart handler which restarts the SoC using the
SRC SW_RST bit.

Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Shawn Guo <shawn.guo@linaro.org>