xps: Add CONFIG_XPS

This patch adds XPS_CONFIG option to enable and disable XPS.  This is
done in the same manner as RPS_CONFIG.  This is also fixes build
failure in XPS code when SMP is not enabled.

Signed-off-by: Tom Herbert <therbert@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/core/net-sysfs.h

@@ -4,11 +4,8 @@
 int netdev_kobject_init(void);
 int netdev_register_kobject(struct net_device *);
 void netdev_unregister_kobject(struct net_device *);
-#ifdef CONFIG_RPS
 int net_rx_queue_update_kobjects(struct net_device *, int old_num, int new_num);
 int netdev_queue_update_kobjects(struct net_device *net,
 				 int old_num, int new_num);
 
 #endif
-
-#endif