nvmet-tcp: fix header digest verification

Pass the correct length to nvmet_tcp_verify_hdgst, which is the pdu
header length.  This fixes a wrong behaviour where header digest
verification passes although the digest is wrong.

Signed-off-by: Amit Engel <amit.engel@dell.com>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Signed-off-by: Christoph Hellwig <hch@lst.de>

drivers/nvme/target/tcp.c

@@ -1096,7 +1096,7 @@ recv:
 	}
 
 	if (queue->hdr_digest &&
-	    nvmet_tcp_verify_hdgst(queue, &queue->pdu, queue->offset)) {
+	    nvmet_tcp_verify_hdgst(queue, &queue->pdu, hdr->hlen)) {
 		nvmet_tcp_fatal_error(queue); /* fatal */
 		return -EPROTO;
 	}