net: hns3: refactor dump mac list of debugfs

Currently, the debugfs command for mac list info is implemented
by "echo xxxx > cmd", and record the information in dmesg. It's
unnecessary and heavy. To improve it, create two files "uc" and
"mc" under directory "mac_list" for it, and query mac list info
by "cat mac_list/uc" and "mac_list/mc", return the result to
userspace, rather than record in dmesg.

The display style is below:
$ cat mac_list/uc
UC MAC_LIST:
FUNC_ID  MAC_ADDR            STATE
pf       00:18:2d:00:00:71   ACTIVE

$ cat mac_list/mc
MC MAC_LIST:
FUNC_ID  MAC_ADDR            STATE
pf       01:80:c2:00:00:21   ACTIVE

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