[SCSI] libiscsi, iscsi_tcp, iser: add session cmds array accessor

Currently to get a ctask from the session cmd array, you have to
know to use the itt modifier. To make this easier on LLDs and
so in the future we can easilly kill the session array and use
the host shared map instead, this patch adds a nice wrapper
to strip the itt into a session->cmds index and return a ctask.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/include/scsi/libiscsi.h b/include/scsi/libiscsi.h
index f54aeb1..9be6a70 100644
--- a/include/scsi/libiscsi.h
+++ b/include/scsi/libiscsi.h
@@ -385,8 +385,8 @@
 				char *, uint32_t);
 extern int iscsi_complete_pdu(struct iscsi_conn *, struct iscsi_hdr *,
 			      char *, int);
-extern int iscsi_verify_itt(struct iscsi_conn *, struct iscsi_hdr *,
-			    uint32_t *);
+extern int iscsi_verify_itt(struct iscsi_conn *, itt_t);
+extern struct iscsi_cmd_task *iscsi_itt_to_ctask(struct iscsi_conn *, itt_t);
 extern void iscsi_requeue_ctask(struct iscsi_cmd_task *ctask);
 extern void iscsi_free_mgmt_task(struct iscsi_conn *conn,
 				 struct iscsi_mgmt_task *mtask);