[SCSI] iscsi_tcp: prepare helpers for LLDs that can offload some operations

cxgb3i is unlike qla4xxx and bnx2i in that it does not offload entire
scsi commands or iscsi sequences. Instead it only offloads the transfer
of a ISCSI DATA_IN pdu's data, the digests and padding. This patch fixes up the
iscsi tcp recv path so that it exports its skb recv processing so
cxgb3i and other drivers can call them. All they have to do is pass
the function the skb with the hdr or data pdu header and this function
will do the rest.

Signed-off-by: Mike Christie <michaelc@cs.wisc.edu>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
diff --git a/include/scsi/iscsi_if.h b/include/scsi/iscsi_if.h
index 0c9514d..8e008c9 100644
--- a/include/scsi/iscsi_if.h
+++ b/include/scsi/iscsi_if.h
@@ -333,8 +333,9 @@
 #define CAP_TEXT_NEGO		0x80
 #define CAP_MARKERS		0x100
 #define CAP_FW_DB		0x200
-#define CAP_SENDTARGETS_OFFLOAD	0x400
-#define CAP_DATA_PATH_OFFLOAD	0x800
+#define CAP_SENDTARGETS_OFFLOAD	0x400	/* offload discovery process */
+#define CAP_DATA_PATH_OFFLOAD	0x800	/* offload entire IO path */
+#define CAP_DIGEST_OFFLOAD	0x1000	/* offload hdr and data digests */
 
 /*
  * These flags describes reason of stop_conn() call