RDMA/hns: Add constraint on the setting of local ACK timeout

According to IB protocol, local ACK timeout shall be a 5 bit
value. Currently, hip08 could not support the possible max value 31. Fail
the request in this case.

Signed-off-by: Yixian Liu <liuyixian@huawei.com>
Signed-off-by: Lijun Ou <oulijun@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>