Use state table to make the qp state migrate code more readable.

Link: https://lore.kernel.org/r/1586938475-37049-6-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@mellanox.com>