scsi: target: iscsi: Rename iscsi_conn to iscsit_conn

The structure iscsi_conn naming is used by the iSCSI initiator
driver. Rename the target conn to iscsit_conn to have more readable code.

Link: https://lore.kernel.org/r/20220428092939.36768-2-mgurtovoy@nvidia.com


Reviewed-by: Mike Christie <michael.christie@oracle.com>
Signed-off-by: Max Gurtovoy <mgurtovoy@nvidia.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>