arm64: dts: add dwmmc nodes for hi6220

Add all three dwmmc nodes description for hi6220

Signed-off-by: Guodong Xu <guodong.xu@linaro.org>
Signed-off-by: Xinwei Kong <kong.kongxinwei@hisilicon.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>