RDMA/hns: Bugfix for calculation of extended sge

RDMA/hns: Bugfix for calculation of extended sge

Page alignment is required when setting the number of extended sge
according to the hardware's achivement. If the space of needed extended
sge is greater than one page, the roundup_pow_of_two() can ensure
that. But if the needed extended sge isn't 0 and can not be filled in a
whole page, the driver should align it specifically.

Fixes: 54d6638765b0 ("RDMA/hns: Optimize WQE buffer size calculating process")
Link: https://lore.kernel.org/r/1606558959-48510-3-git-send-email-liweihang@huawei.com
Signed-off-by: Yangyang Li <liyangyang20@huawei.com>
Signed-off-by: Weihang Li <liweihang@huawei.com>
Reviewed-by: Leon Romanovsky <leonro@nvidia.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>