dt-bindings: arm-smmu: Add sm8350 compatible string

Add compatible string for sm8350 iommu to documentation.

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20210115090322.2287538-1-vkoul@kernel.org


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