net: hns3: use pause capability queried from firmware

For maintainability and compatibility, add support to use pause
capability queried from firmware, and add debugfs support to dump
this capability.

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