net-next/hinic: Add cmdq completion handler

Add cmdq completion handler for getting a notification about the
completion of cmdq commands.

Signed-off-by: Aviad Krawczyk <aviad.krawczyk@huawei.com>
Signed-off-by: Zhao Chen <zhaochen6@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>