[NET]: Make and use skb_get_queue_mapping

Make the helper for getting the field, symmetrical to
the "set" one. Return 0 if CONFIG_NETDEVICES_MULTIQUEUE=n

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 369f60a..ecb0ede 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1769,6 +1769,15 @@
 #endif
 }
 
+static inline u16 skb_get_queue_mapping(struct sk_buff *skb)
+{
+#ifdef CONFIG_NETDEVICES_MULTIQUEUE
+	return skb->queue_mapping;
+#else
+	return 0;
+#endif
+}
+
 static inline void skb_copy_queue_mapping(struct sk_buff *to, const struct sk_buff *from)
 {
 #ifdef CONFIG_NETDEVICES_MULTIQUEUE