RDMA/srpt: Increase max_send_sge

The ib_srpt driver limits max_send_sge to 16. Since that is a workaround
for an mlx4 bug that has been fixed, increase max_send_sge. See also
commit f95ccffc ("IB/mlx4: Use 4K pages for kernel QP's WQE buffer").

Link: https://lore.kernel.org/r/20200525172212.14413-5-bvanassche@acm.org


Signed-off-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Jason Gunthorpe <jgg@mellanox.com>