psp: do not use sk_dst_get() in psp_dev_get_for_sock()

psp: do not use sk_dst_get() in psp_dev_get_for_sock()

Use __sk_dst_get() and dst_dev_rcu(), because dst->dev could
be changed under us.

Fixes: 6b46ca260e22 ("net: psp: add socket security association code")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willem de Bruijn <willemb@google.com>
Tested-by: Daniel Zahka <daniel.zahka@gmail.com>
Reviewed-by: Daniel Zahka <daniel.zahka@gmail.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@google.com>
Link: https://patch.msgid.link/20250918115238.237475-1-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>