dt-bindings: arm-smmu: document the smmu on Qualcomm SA8775P

Document the qcom,smmu-500 SMMU on SA8775P platforms.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230112154554.442808-1-brgl@bgdev.pl


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