s390/qeth: try harder to get packets from RX buffer

Current code bails out when two subsequent buffer elements hold
insufficient data to contain a qeth_hdr packet descriptor.
This seems reasonable, but it would be legal for quirky hardware to
leave a few elements empty and then present packets in a subsequent
element. These packets would currently be dropped.

So make sure to check all buffer elements, until we hit the LAST_ENTRY
indication.
Signed-off-by: Julian Wiedmann <jwi@linux.vnet.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core_main.c

@@ -5214,13 +5214,11 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 	int use_rx_sg = 0;
 
 	/* qeth_hdr must not cross element boundaries */
-	if (element->length < offset + sizeof(struct qeth_hdr)) {
+	while (element->length < offset + sizeof(struct qeth_hdr)) {
 		if (qeth_is_last_sbale(element))
 			return NULL;
 		element++;
 		offset = 0;
-		if (element->length < sizeof(struct qeth_hdr))
-			return NULL;
 	}
 	*hdr = element->addr + offset;