net: also flag accepted sockets supporting msghdr originated zerocopy

Without this only the client initiated tcp sockets have SOCK_SUPPORT_ZC.
The listening socket on the server also has it, but the accepted
connections didn't, which meant IORING_OP_SEND[MSG]_ZC will always
fails with -EOPNOTSUPP.

Fixes: e993ffe3 ("net: flag sockets supporting msghdr originated zerocopy")
Cc: <stable@vger.kernel.org> # 6.0
CC: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/io-uring/20221024141503.22b4e251@kernel.org/T/#m38aa19b0b825758fb97860a38ad13122051f9ddaSigned-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/ipv4/af_inet.c

@@ -754,6 +754,8 @@ int inet_accept(struct socket *sock, struct socket *newsock, int flags,
 		  (TCPF_ESTABLISHED | TCPF_SYN_RECV |
 		  TCPF_CLOSE_WAIT | TCPF_CLOSE)));
 
+	if (test_bit(SOCK_SUPPORT_ZC, &sock->flags))
+		set_bit(SOCK_SUPPORT_ZC, &newsock->flags);
 	sock_graft(sk2, newsock);
 
 	newsock->state = SS_CONNECTED;