IB/isert: use the ISCSI_LOGIN_CURRENT_STAGE macro

Use the proper macro to get the current_stage value.

Link: https://lore.kernel.org/r/20221116094535.138298-1-mlombard@redhat.com


Signed-off-by: Maurizio Lombardi <mlombard@redhat.com>
Reviewed-by: Mike Christie <michael.christie@oracle.com>
Acked-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Jason Gunthorpe <jgg@nvidia.com>