ARM: dts: renesas: kzm9g: Use interrupts-extended for I/O expander

Use the more concise interrupts-extended property to fully describe the
interrupt.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
Reviewed-by: Niklas Söderlund <niklas.soderlund+renesas@ragnatech.se>
Reviewed-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Link: https://lore.kernel.org/c77ffcd01d6e9e90cd1e5578c2af98c9ec6030c9.1728045620.git.geert+renesas@glider.be