CIFS: Separate SMB2 sync header processing

Do not process RFC1001 length in smb2_hdr_assemble() because
it is not a part of SMB2 header. This allows to cleanup the code
and adds a possibility combine several SMB2 packets into one
for compounding.

Signed-off-by: Pavel Shilovsky <pshilov@microsoft.com>
diff --git a/fs/cifs/smb2pdu.h b/fs/cifs/smb2pdu.h
index 8dd24b7..052342d 100644
--- a/fs/cifs/smb2pdu.h
+++ b/fs/cifs/smb2pdu.h
@@ -117,6 +117,11 @@ struct smb2_sync_hdr {
 	__u8   Signature[16];
 } __packed;
 
+struct smb2_sync_pdu {
+	struct smb2_sync_hdr sync_hdr;
+	__le16 StructureSize2; /* size of wct area (varies, request specific) */
+} __packed;
+
 struct smb2_hdr {
 	__be32 smb2_buf_length;	/* big endian on wire */
 				/* length is only two or three bytes - with */