dt-bindings: memory: convert Broadcom DPFE to dtschema

Convert Broadcom DDR PHY Front End (DPFE) bindings to DT schema format
using json-schema.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Acked-by: Markus Mayer <mmayer@broadcom.com>
Link: https://lore.kernel.org/r/20210817080617.14503-1-krzysztof.kozlowski@canonical.com


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