Add the apps_smmu node for sm8250.

For UFS, now that the kernel initializes the iommu, the stream mappings
set by the bootloader are cleared. Adding the iommus property is required
so that new mappings are created for UFS.
Signed-off-by: Jonathan Marek <jonathan@marek.ca>
Link: https://lore.kernel.org/r/20200609194030.17756-5-jonathan@marek.caSigned-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>