qeth: core code should alloc headroom for LLC protocol

Allocate headroom for TR_HLEN but using only ETH_HLEN causes rx
performance degradation. Allocate ETH_HLEN for ethernet and
TR_HLEN for token ring (layer 3 mode).
Signed-off-by: NFrank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: NJeff Garzik <jgarzik@redhat.com>

drivers/s390/net/qeth_core_main.c

@@ -4002,7 +4002,11 @@ struct sk_buff *qeth_core_get_next_skb(struct qeth_card *card,
 		}
 	} else {
 		skb_len = (*hdr)->hdr.l3.length;
-		headroom = max((int)ETH_HLEN, (int)TR_HLEN);
+		if ((card->info.link_type == QETH_LINK_TYPE_LANE_TR) ||
+		    (card->info.link_type == QETH_LINK_TYPE_HSTR))
+			headroom = TR_HLEN;
+		else
+			headroom = ETH_HLEN;
 	}
 
 	if (!skb_len)