Document: dw_mmc-k3: add document of hi6220 mmc

Add bindings for hi6220 mmc support

Signed-off-by: Zhangfei Gao <zhangfei.gao@linaro.org>
Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Signed-off-by: Ulf Hansson <ulf.hansson@linaro.org>
1 file changed