dt-bindings: iommu: mediatek: add binding documentation for MT8365 SoC

Add IOMMU binding documentation for the MT8365 SoC.

Signed-off-by: Fabien Parent <fparent@baylibre.com>
Signed-off-by: Markus Schneider-Pargmann <msp@baylibre.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Yong Wu <yong.wu@mediatek.com>
Signed-off-by: Alexandre Mergnat <amergnat@baylibre.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/20221001-iommu-support-v6-1-be4fe8da254b@baylibre.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>