IB/srp: fix invalid indirect_sg_entries parameter value

After setting indirect_sg_entries module_param to huge value (e.g 500,000),
srp_alloc_req_data() fails to allocate indirect descriptors for the request
ring (kmalloc fails). This commit enforces the maximum value of
indirect_sg_entries to be SG_MAX_SEGMENTS as signified in module param
description.

Fixes: 65e8617f (scsi: rename SCSI_MAX_{SG, SG_CHAIN}_SEGMENTS)
Fixes: c07d424d

 (IB/srp: add support for indirect tables that don't fit in SRP_CMD)
Cc: stable@vger.kernel.org # 4.7+
Signed-off-by: Israel Rukshin <israelr@mellanox.com>
Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Reviewed-by: Laurence Oberman <loberman@redhat.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com&gt;-->
Signed-off-by: Doug Ledford <dledford@redhat.com>