Some commands are not supported on DCB-unsupported ports.
This patch distinguishes these commands and does not query
unsupported commands in debugfs.

This patch also fix an error in the dump "qos buf cfg"
command in debugfs.

Fixes: 2849d4e7 ("net: hns3: Add "tc config" info query function")
Fixes: 7d9d7f88 ("net: hns3: Add "qos buffer" config info query function")
Signed-off-by: Yufeng Mo <moyufeng@huawei.com>
Reviewed-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>