dt-bindings: memory: fsl: convert DDR controller to dtschema

Convert Freescale/NXP DDR memory controller bindings to DT schema format
using json-schema.

Previous bindings were not listing all compatibles, so scan through
devicetree sources and drivers to get these.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Link: https://lore.kernel.org/r/20210826113049.92962-1-krzysztof.kozlowski@canonical.com
Signed-off-by: Rob Herring <robh@kernel.org>