dt-bindings: memory: tegra124: mc: Document new interconnect property

dt-bindings: memory: tegra124: mc: Document new interconnect property

Memory controller is interconnected with memory clients and with the
External Memory Controller. Document new interconnect property which
turns memory controller into interconnect provider.

Signed-off-by: Dmitry Osipenko <digetx@gmail.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20201104164923.21238-13-digetx@gmail.com
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>