net: hns3: refactor dump qos pause cfg of debugfs

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

To optimize it, create a single file "qos_pause_cfg" 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_pause_cfg
pause_trans_gap: 0x7f
pause_trans_time: 0xffff

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>