dt-bindings: memory: convert TI a8xx DDR2/mDDR memory controller to dtschema

Convert Texas Instruments da8xx DDR2/mDDR memory controller bindings to
DT schema format using json-schema.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210818113248.85084-1-krzysztof.kozlowski@canonical.com


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