The max_srq_desc_sz is defined in the code, but never used,
so delete this redundant variable.

Link: https://lore.kernel.org/r/20220922123315.3732205-10-xuhaoyue1@hisilicon.comSigned-off-by: Yangyang Li <liyangyang20@huawei.com>
Signed-off-by: Haoyue Xu <xuhaoyue1@hisilicon.com>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>