Add a node for the APPS SMMU to allow for managing memory access to peripherals
such as the USB controller.

While at it, add iommus property to the USB1 node to make sure its registers can
be accessed, as they seem to be gated by default.
Signed-off-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Link: https://lore.kernel.org/r/20210923162204.21752-15-konrad.dybcio@somainline.org