arm64: dts: qcom: sm8550: add specific SMMU compatible

Generic SMMU compatibles are not allowed alone and we expect specific
one.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230127115513.268843-1-krzysztof.kozlowski@linaro.org