dt-bindings: mmc: convert rockchip dw-mshc bindings to yaml

dt-bindings: mmc: convert rockchip dw-mshc bindings to yaml

Current dts files with 'dwmmc' nodes are manually verified.
In order to automate this process rockchip-dw-mshc.txt
has to be converted to yaml. In the new setup
rockchip-dw-mshc.yaml will inherit properties from
mmc-controller.yaml and synopsys-dw-mshc-common.yaml.
'dwmmc' will no longer be a valid name for a node and
should be changed to 'mmc'.

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20200116152230.29831-2-jbx6244@gmail.com
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>