arm64: dts: renesas: r9a09g087: Add ICU support

arm64: dts: renesas: r9a09g087: Add ICU support

The Renesas RZ/N2H (R9A09G087) SoC has an Interrupt Controller (ICU)
block that routes external interrupts to the GIC's SPIs, with the
ability of level-translation, and can also produce software and
aggregate error interrupts.

Add support for it.

Signed-off-by: Cosmin Tanislav <cosmin-gabriel.tanislav.xa@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Link: https://patch.msgid.link/20251201112933.488801-5-cosmin-gabriel.tanislav.xa@renesas.com
Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>