memory: tegra: Only initialize reset controller if available

The memory controller hot resets are implemented in the BPMP on Tegra186
and later, so there's no need to provide an implementation via the
memory controller driver. Conditionally register the reset controller
only if needed.

Signed-off-by: Thierry Reding <treding@nvidia.com>
Link: https://lore.kernel.org/r/20210602163302.120041-10-thierry.reding@gmail.com


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