dt-bindings: iommu: arm-smmu: add sdm670 compatible

The Snapdragon 670 needs the IOMMU for GENI I2C. Add a compatible string in
the documentation to represent its support.

Signed-off-by: Richard Acayan <mailingradian@gmail.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20221111003606.126795-2-mailingradian@gmail.com


Signed-off-by: Will Deacon <will@kernel.org>