net: hns3: remove unnecessary work in hclgevf_main

There are four work (mbx_service_task, service_task,
rst_service_task and keep_alive_task)in the hclgevf module,
mbx_service_task is for handling mailbox issue, service_task is
for periodic management issue and rst_service_task is for reset
related issue, keep_alive_task is used to keepalive between PF
and VF, which can be done in a single work.

This patch removes the mbx_service_task, rst_service_task and
keep_alive_task, and moves the related handling to the
service_task work in order to remove concurrency between the four
work and to improve efficiency.

Signed-off-by: Yunsheng Lin <linyunsheng@huawei.com>
Signed-off-by: Huazhong Tan <tanhuazhong@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>