RDMA/hns: Check if depth of qp is 0 before configure

Depth of qp shouldn't be allowed to be set to zero, after ensuring that,
subsequent process can be simplified. And when qp is changed from reset to
reset, the capability of minimum qp depth was used to identify hardware of
hip06, it should be changed into a more readable form.

Link: https://lore.kernel.org/r/1584006624-11846-1-git-send-email-liweihang@huawei.com


Signed-off-by: Lang Cheng <chenglang@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>