Fix error of cmd's context number calculation algorithm to enable all of
32 cmd entries and support 32 concurrent accesses.

Link: https://lore.kernel.org/r/1617262341-37571-2-git-send-email-liweihang@huawei.comSigned-off-by: Lang Cheng <chenglang@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>