dt-bindings: PCI: mediatek-gen3: add SoC based clock config

The PCIe driver covers different SOC which needing different clock
configs. Define them based on compatible.

Link: https://lore.kernel.org/r/20221127114142.156573-4-linux@fw-web.de


Signed-off-by: Frank Wunderlich <frank-w@public-files.de>
Signed-off-by: Lorenzo Pieralisi <lpieralisi@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
Acked-by: Jianjun Wang <jianjun.wang@mediatek.com>