dt-bindings: ufs: mediatek,ufs: convert to dtschema

Convert the Mediatek Universal Flash Storage (UFS) Controller to DT
schema format.

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20220306111125.116455-8-krzysztof.kozlowski@canonical.com