ARM: dts: rockchip: rename dwmmc node names to mmc

ARM: dts: rockchip: rename dwmmc node names to mmc

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,
so change them all to 'mmc'

Signed-off-by: Johan Jonker <jbx6244@gmail.com>
Link: https://lore.kernel.org/r/20200115185244.18149-1-jbx6244@gmail.com
Signed-off-by: Heiko Stuebner <heiko@sntech.de>