[SCSI] iscsi: increment expstatsn during login

debugged by Ming and Rohan:

The problem Ming and Rohan debugged was that during a normal session
login, open-iscsi is not incrementing the exp_statsn counter. It was
stuck at zero. From the RFC, it looks like if the login response PDU has
a successful status then we should be incrementing that value. Also from
the RFC, it looks like if when we drop a connection then reconnect, we
should be using the exp_statsn from the old connection in the next
relogin attempt.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@SteelEye.com>
diff --git a/include/scsi/iscsi_if.h b/include/scsi/iscsi_if.h
index feff74e..253797c 100644
--- a/include/scsi/iscsi_if.h
+++ b/include/scsi/iscsi_if.h
@@ -188,6 +188,7 @@
 	ISCSI_PARAM_ERL,
 	ISCSI_PARAM_IFMARKER_EN,
 	ISCSI_PARAM_OFMARKER_EN,
+	ISCSI_PARAM_EXP_STATSN,
 	ISCSI_PARAM_TARGET_NAME,
 	ISCSI_PARAM_TPGT,
 	ISCSI_PARAM_PERSISTENT_ADDRESS,
@@ -216,6 +217,7 @@
 #define ISCSI_ERL			(1 << ISCSI_PARAM_ERL)
 #define ISCSI_IFMARKER_EN		(1 << ISCSI_PARAM_IFMARKER_EN)
 #define ISCSI_OFMARKER_EN		(1 << ISCSI_PARAM_OFMARKER_EN)
+#define ISCSI_EXP_STATSN		(1 << ISCSI_PARAM_EXP_STATSN)
 #define ISCSI_TARGET_NAME		(1 << ISCSI_PARAM_TARGET_NAME)
 #define ISCSI_TPGT			(1 << ISCSI_PARAM_TPGT)
 #define ISCSI_PERSISTENT_ADDRESS	(1 << ISCSI_PARAM_PERSISTENT_ADDRESS)