dts: riscv: starfive: align clint description with Linux

The CLINT (Core Local Interruptor) description was not aligned with
Linux. For example, there's no "riscv,clint0", but "sifive,clint0". The
peripheral is not described as an interrupt-controller either.

Ref. https://elixir.bootlin.com/linux/v5.18.14/source/arch/riscv/boot/


dts/starfive/jh7100.dtsi#L106

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