mptcp: Reorder fields in 'struct mptcp_pm_add_entry'

Group some variables based on their sizes to reduce hole and avoid padding.
On x86_64, this shrinks the size of 'struct mptcp_pm_add_entry'
from 136 to 128 bytes.

It saves a few bytes of memory and is more cache-line friendly.
Signed-off-by: Christophe JAILLET <christophe.jaillet@wanadoo.fr>
Reviewed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/e47b71de54fd3e580544be56fc1bb2985c77b0f4.1687081558.git.christophe.jaillet@wanadoo.frSigned-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/pm_netlink.c

@@ -25,9 +25,9 @@ static int pm_nl_pernet_id;
 struct mptcp_pm_add_entry {
 	struct list_head	list;
 	struct mptcp_addr_info	addr;
+	u8			retrans_times;
 	struct timer_list	add_timer;
 	struct mptcp_sock	*sock;
-	u8			retrans_times;
 };
 
 struct pm_nl_pernet {