iommu/arm-smmu: tegra: Detect number of instances at runtime

Parse the reg property in device tree and detect the number of instances
represented by a device tree node. This is subsequently needed in order
to support single-instance SMMUs with the Tegra implementation because
additional programming is needed to properly configure the SID override
registers in the memory controller.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20210603164632.1000458-5-thierry.reding@gmail.com


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>