dt-bindings: perf: Convert i.MX DDR to json-schema

Convert the i.MX DDR perf binding to DT schema format using json-schema.

Signed-off-by: Anson Huang <Anson.Huang@nxp.com>
Link: https://lore.kernel.org/r/1596609387-23542-1-git-send-email-Anson.Huang@nxp.com


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