RDMA/hns: reset function when removing module

During removing the driver, we needs to notify the roce engine to
stop working immediately,and symmetrically recycle the hardware
resources requested during initialization.

The hardware provides a command called function clear that can package
these operations,so that the driver can only focus on releasing
resources that applied from the operating system.
This patch implements the call of this command.

Signed-off-by: Lang Cheng <chenglang@huawei.com>
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>