IB/iser: remove unused variable from iser_conn struct

max_sectors calculation was fixed in commit:
9c674815

 ("IB/iser: Fix max_sectors calculation").
Thus, iser_conn variable scsi_max_sectors is not needed anymore.

Signed-off-by: Max Gurtovoy <maxg@mellanox.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Tested-by: Raju Rangoju <rajur@chelsio.com>
Signed-off-by: Doug Ledford <dledford@redhat.com>