phonet: fix rtm_phonet_notify() skb allocation

phonet: fix rtm_phonet_notify() skb allocation

fill_route() stores three components in the skb:

- struct rtmsg
- RTA_DST (u8)
- RTA_OIF (u32)

Therefore, rtm_phonet_notify() should use

NLMSG_ALIGN(sizeof(struct rtmsg)) +
nla_total_size(1) +
nla_total_size(4)

Fixes: f062f41d0657 ("Phonet: routing table Netlink interface")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Acked-by: Rémi Denis-Courmont <courmisch@gmail.com>
Link: https://lore.kernel.org/r/20240502161700.1804476-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>