net: hns3: add missing help info for QS shaper in debugfs

HNS3 driver can dump QS shaper configs via debugfs, but missing
help info in debugfs for this operation.

Signed-off-by: Yonglong Liu <liuyonglong@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>