net: hns3: refactor dump qos pri map of debugfs

Currently, user gets priority map by implementing debugfs command
"echo dump qos pri map > cmd", this command will dump info in dmesg.
It's unnecessary and heavy.

To optimize it, create a single file "qos_pri_map" in tm directory
and use cat command to get info. It will return info to userspace,
rather than record in dmesg.

The display style is below:
$ cat qos_pri_map
vlan_to_pri: 0
PRI    TC
0       0
1       1
2       2
3       3
4       0
5       1
6       2

Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>