net: hns3: add support for dump ncl config by debugfs

This patch allow users to dump content of NCL_CONFIG by using debugfs
command.
Command format:
	echo dump ncl_config <offset> <length> > cmd
It will print as follows:
	hns3 0000:7d:00.0: offset |    data
	hns3 0000:7d:00.0: 0x0000 | 0x00000020
	hns3 0000:7d:00.0: 0x0004 | 0x00000400
	hns3 0000:7d:00.0: 0x0008 | 0x08020401

Signed-off-by: Weihang Li <liweihang@hisilicon.com>
Signed-off-by: Peng Li <lipeng321@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>