net: hns3: add support for FD counter in debugfs

Previously, the flow director counter is not enabled. To improve the
maintainability for chechking whether flow director hit or not, enable
flow director counter for each function, and add debugfs query inerface
to query the counters for each function.

The debugfs command is below:
cat fd_counter
func_id    hit_times
pf         0
vf0        0
vf1        0

Signed-off-by: Jian Shen <shenjian15@huawei.com>
Signed-off-by: Guangbin Huang <huangguangbin2@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>