net: Annotate sk->sk_write_space() for UDP SOCKMAP.

net: Annotate sk->sk_write_space() for UDP SOCKMAP.

UDP TX skb->destructor() is sock_wfree(), and UDP holds lock_sock()
only for UDP_CORK / MSG_MORE sendmsg().

Otherwise, sk->sk_write_space() may be read locklessly while SOCKMAP
rewrites sk->sk_write_space().

Let's use WRITE_ONCE() and READ_ONCE() for sk->sk_write_space().

Note that the write side is annotated by commit 2ef2b20cf4e0
("net: annotate data-races around sk->sk_{data_ready,write_space}").

Fixes: 7b98cd42b049 ("bpf: sockmap: Add UDP support")
Signed-off-by: Kuniyuki Iwashima <kuniyu@google.com>
Reviewed-by: Jakub Sitnicki <jakub@cloudflare.com>
Link: https://patch.msgid.link/20260529193941.3897256-1-kuniyu@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>