arm64: tegra: Hook up memory controller to SMMU on Tegra186

On Tegra186 and later, the memory controller needs to be programmed in
coordination with any of the ARM SMMU instances to configure the stream
ID used for each memory client.

To support this, add a phandle reference to the memory controller to the
SMMU device tree node.

Signed-off-by: Thierry Reding <treding@nvidia.com>