netif_set_xps_queue: make cpu mask const

virtio wants to pass in cpumask_of(cpu), make parameter
const to avoid build warnings.

Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 3de49ac..25f5d2d 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -2264,11 +2264,12 @@
 }
 
 #ifdef CONFIG_XPS
-extern int netif_set_xps_queue(struct net_device *dev, struct cpumask *mask,
+extern int netif_set_xps_queue(struct net_device *dev,
+			       const struct cpumask *mask,
 			       u16 index);
 #else
 static inline int netif_set_xps_queue(struct net_device *dev,
-				      struct cpumask *mask,
+				      const struct cpumask *mask,
 				      u16 index)
 {
 	return 0;