Add devicetree binding for Hisilicon SD5203 SoC.

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
Link: https://lore.kernel.org/r/20200929141454.2312-6-thunder.leizhen@huawei.com


Signed-off-by: Rob Herring <robh@kernel.org>