dt-bindings: spmi: spmi-mtk-pmif: Document mediatek,mt8195-spmi as fallback of mediatek,mt8186-spmi

The mt8186-spmi is used as compatible with mt8195-spmi on the MT8186,
document this situation.

Signed-off-by: Allen-KH Cheng <allen-kh.cheng@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Link: https://lore.kernel.org/r/20230324021258.15863-3-allen-kh.cheng@mediatek.com


Signed-off-by: Matthias Brugger <matthias.bgg@gmail.com>