net: hisilicon: updates HNS config and documents

updates the bindings documents and dtsi file according to the review
comments[https://lkml.org/lkml/2015/9/21/670] from Rob Herring <robh@kernel.org>

Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: yankejian <yankejian@huawei.com>
Signed-off-by: huangdaode <huangdaode@hisilicon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>