qeth: Fix IP version detection for VLAN traffic

The current code would always return 0 for VLAN-encapsulated IP traffic.
One notable side effect was that VLAN traffic would never get prioritized
on OSD and OSX devices when priority queueing modes prio_queueing_tos or
prio_queueing_prec were enabled.

Signed-off-by: Stefan Raspl <raspl@linux.vnet.ibm.com>
Signed-off-by: Frank Blaschka <frank.blaschka@de.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/s390/net/qeth_core.h

@@ -854,8 +854,11 @@ static inline int qeth_get_micros(void)
 
 static inline int qeth_get_ip_version(struct sk_buff *skb)
 {
-	struct ethhdr *ehdr = (struct ethhdr *)skb->data;
-	switch (ehdr->h_proto) {
+	__be16 *p = &((struct ethhdr *)skb->data)->h_proto;
+
+	if (*p == ETH_P_8021Q)
+		p += 2;
+	switch (*p) {
 	case ETH_P_IPV6:
 		return 6;
 	case ETH_P_IP: