soc: arch: synopsys: move timer0/1 IRQ information to DT

timer0/1 IRQ information was hardcoded in soc.h, however, Devicetree is
nowadays a better place to describe hardware. Note that I have followed
existing upstream Linux code to do these changes.

Ref.
- https://elixir.bootlin.com/linux/latest/source/arch/arc/boot/dts/
  hsdk.dts
- https://elixir.bootlin.com/linux/latest/source/Documentation/
  devicetree/bindings/timer/snps,arc-timer.txt

Signed-off-by: Gerard Marull-Paretas <gerard.marull@nordicsemi.no>