irqchip/irq-mtk-cirq: Add support for System CIRQ on MT8192

On some SoCs the System CIRQ register layout is slightly different,
as there are more registers per function and in some cases other
differences later in the layout: this is seen on at least MT8192,
but it's also valid for some other "contemporary" SoCs both for
Chromebooks and for smartphones.

Add the new "v2" register layout and use it if the compatible
"mediatek,mt8192-cirq" is found.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20221128092217.36552-5-angelogioacchino.delregno@collabora.com