aspeed: Update ast2500 Device Tree

Pull in the Device Tree for ast2500 from the mainline Linux kernel.
The file is copied from
https://raw.githubusercontent.com/torvalds/linux/34ea5c9d/arch/arm/boot/dts/aspeed-g5.dtsi



Signed-off-by: Maxim Sloyko <maxims@google.com>
Reviewed-by: Simon Glass <sjg@chromium.org>