arm: dts: qcom: sc7180: Set the compatible string for the GPU SMMU

Set the qcom,adreno-smmu compatible string for the GPU SMMU to enable
split pagetables and per-instance pagetables for drm/msm.

Signed-off-by: Rob Clark <robdclark@chromium.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20200905200454.240929-21-robdclark@gmail.com


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>