net/hns3: fix secondary process reference count

net/hns3: fix secondary process reference count

The "secondary_cnt" will be increased when a secondary process
initialized. But the value of this variable is not decreased when the
secondary process exits, which causes the primary process senses that
the secondary process still exists. As a result, the primary process
fails to send messages to the secondary process after the secondary
process exits.

Fixes: 23d4b61fee5d ("net/hns3: support multiple process")
Cc: stable@dpdk.org
Signed-off-by: Huisong Li <lihuisong@huawei.com>
Signed-off-by: Min Hu (Connor) <humin29@huawei.com>