The ARM SMMU instantiations found on Tegra186 and later need inter-
operation with the memory controller in order to correctly program
stream ID overrides.

Furthermore, on Tegra194 multiple instances of the SMMU can gang up
to achieve higher throughput. In order to do this, they have to be
programmed identically so that the memory controller can interleave
memory accesses between them.

Add the Tegra186 compatible string to make sure the interoperation
with the memory controller can be enabled on that SoC generation.
Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20210603164632.1000458-3-thierry.reding@gmail.comSigned-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>