RDMA/hns: Correct the value of srq_desc_size

RDMA/hns: Correct the value of srq_desc_size

srq_desc_size should be rounded up to pow of two before used, or related
calculation may cause allocating wrong size of memory for srq buffer.

Fixes: fbe6e729ac72 ("RDMA/hns: Add SRQ support for hip08 kernel mode")
Link: https://lore.kernel.org/r/1572575610-52530-3-git-send-email-liweihang@hisilicon.com
Signed-off-by: Wenpeng Liang <liangwenpeng@huawei.com>
Signed-off-by: Weihang Li <liweihang@hisilicon.com>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>