RDMA/hns: WARN_ON if get a reserved sl from users

According to the RoCE v1 specification, the sl (service level) 0-7 are
mapped directly to priorities 0-7 respectively, sl 8-15 are reserved. The
driver should verify whether the value of sl is larger than 7, if so, an
exception should be returned.

Link: https://lore.kernel.org/r/1607650657-35992-6-git-send-email-liweihang@huawei.com


Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>