dt-bindings: mmc: convert arasan sdhci bindings to yaml

dt-bindings: mmc: convert arasan sdhci bindings to yaml

Convert arasan,sdhci.txt file to yaml. The new file arasan,sdhci.yaml
will inherit properties from mmc-controller.yaml. 'sdhci' is no longer
a valid name for node and should be changed to 'mmc'.

Suggested-by: Ulf Hansson <ulf.hansson@linaro.org>
Signed-off-by: Wan Ahmad Zainie <wan.ahmad.zainie.wan.mohamad@intel.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200701023346.3873-1-wan.ahmad.zainie.wan.mohamad@intel.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>