RDMA/hns: Remove asynchronic QP destroy

Verbs destroy callbacks are synchronous operations and can't be delayed.
The expectation is that after driver returned from destroy function, the
memory can be freed and user won't be able to access it again.

Ditch workqueue implementation used in HNS driver.

Fixes: d838c481 ("IB/hns: Fix the bug when destroy qp")
Signed-off-by: Leon Romanovsky <leonro@mellanox.com>
Acked-by: oulijun <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>