dt-bindings: Relocate Tegra20 memory controller bindings

Move the device tree bindings for the Tegra20 memory controller to the
same location as the Tegra30 (and later) memory controller bindings.

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

diff --git a/Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-mc.txt b/Documentation/devicetree/bindings/memory-controllers/nvidia,tegra20-mc.txt
similarity index 100%
rename from Documentation/devicetree/bindings/arm/tegra/nvidia,tegra20-mc.txt
rename to Documentation/devicetree/bindings/memory-controllers/nvidia,tegra20-mc.txt