[SCSI] libcxgbi: pdu read fixes

Fixed the locking and releasing skb in the case of error in the pdu
read path, and added define iscsi_task_cxgbi_data to access the
private data inside the iscsi_task.

Signed-off-by: Karen Xie <kxie@chelsio.com>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@suse.de>
diff --git a/drivers/scsi/cxgbi/libcxgbi.h b/drivers/scsi/cxgbi/libcxgbi.h
index 2f2485b..48e6d62 100644
--- a/drivers/scsi/cxgbi/libcxgbi.h
+++ b/drivers/scsi/cxgbi/libcxgbi.h
@@ -592,6 +592,8 @@
 	unsigned int count;
 	unsigned int sgoffset;
 };
+#define iscsi_task_cxgbi_data(task) \
+	((task)->dd_data + sizeof(struct iscsi_tcp_task))
 
 static inline int cxgbi_is_ddp_tag(struct cxgbi_tag_format *tformat, u32 tag)
 {