dt-bindings: memory: convert Marvell MVEBU SDRAM controller to dtschema

Convert Marvell MVEBU SDRAM controller bindings to DT schema format
using json-schema.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210817093807.59531-1-krzysztof.kozlowski@canonical.com


Signed-off-by: Rob Herring <robh@kernel.org>