[SCSI] libiscsi_tcp: support padding offload

cxgb3i does not offload the processing of the header,
but it will always process the padding. This patch
adds a padding offload flag to detect when the LLD
supports this.

The patch also modifies the header processing so that
we do not try to read/bypass the header dugest in the
skb. cxgb3i will not include it with the header like
with other offload cards.

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 8e008c9..d0ed522 100644
--- a/include/scsi/iscsi_if.h
+++ b/include/scsi/iscsi_if.h
@@ -336,6 +336,8 @@
 #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 */
+#define CAP_PADDING_OFFLOAD	0x2000	/* offload padding insertion, removal,
+					 and verification */
 
 /*
  * These flags describes reason of stop_conn() call