Add mt8188 smi supporting in the bindings.

In mt8188, there are two smi-common HW, one is for vdo(video output),
the other is for vpp(video processing pipe). They connect with different
smi-larbs, then some setting(bus_sel) is different. Differentiate them
with the compatible string.

Something like this:

   IOMMU(VDO)          IOMMU(VPP)
       |                   |
SMI_COMMON_VDO       SMI_COMMON_VPP
----------------     ----------------
   |     |   ...       |     |    ...
 larb0 larb2 ...     larb1 larb3  ...
Signed-off-by: Chengci.Xu <chengci.xu@mediatek.com>
Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
Reviewed-by: Yong Wu <yong.wu@mediatek.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220817124608.10062-2-chengci.xu@mediatek.com