netdevice: move xdp_rxq within netdev_rx_queue

Both struct netdev_rx_queue and struct xdp_rxq_info are cacheline
aligned. This causes extra padding before and after the xdp_rxq
member. Move the member upfront, so that it's naturally aligned.

Before:
	/* size: 256, cachelines: 4, members: 6 */
	/* sum members: 160, holes: 1, sum holes: 40 */
	/* padding: 56 */
	/* paddings: 1, sum paddings: 36 */
	/* forced alignments: 1, forced holes: 1, sum forced holes: 40 */

After:
	/* size: 192, cachelines: 3, members: 6 */
	/* padding: 32 */
	/* paddings: 1, sum paddings: 36 */
	/* forced alignments: 1 */

Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Link: https://lore.kernel.org/r/20210823180135.1153608-1-kuba@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

include/linux/netdevice.h

@@ -722,13 +722,13 @@ bool rps_may_expire_flow(struct net_device *dev, u16 rxq_index, u32 flow_id,
 
 /* This structure contains an instance of an RX queue. */
 struct netdev_rx_queue {
+	struct xdp_rxq_info		xdp_rxq;
 #ifdef CONFIG_RPS
 	struct rps_map __rcu		*rps_map;
 	struct rps_dev_flow_table __rcu	*rps_flow_table;
 #endif
 	struct kobject			kobj;
 	struct net_device		*dev;
-	struct xdp_rxq_info		xdp_rxq;
 #ifdef CONFIG_XDP_SOCKETS
 	struct xsk_buff_pool            *pool;
 #endif