dt-bindings: mmc: iproc-sdhci: Convert to json-schema

Convert the brcm,iproc-sdhci binding to DT schema format using json-schema

Signed-off-by: Nicolas Saenz Julienne <nsaenz@kernel.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210406104802.20898-2-nsaenz@kernel.org


Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>