dt-bindings: devfreq: rk3399_dmc: Deprecate unused/redundant properties

These DRAM configuration properties are all handled in ARM Trusted
Firmware (and have been since the early days of this SoC), and there are
no in-tree users of the DMC binding yet. It's better to just defer to
firmware instead of maintaining this large list of properties.

There's also some confusion about units: many of these are specified in
MHz, but the downstream users and driver code are treating them as Hz, I
believe. Rather than straighten all that out, I just drop them.

Signed-off-by: Brian Norris <briannorris@chromium.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Signed-off-by: Chanwoo Choi <cw00.choi@samsung.com>