vsock: Make accept()ed sockets use custom setsockopt()

SO_ZEROCOPY handling in vsock_connectible_setsockopt() does not get called
on accept()ed sockets due to a missing flag. Flip it.

Fixes: e0718bd82e27 ("vsock: enable setting SO_ZEROCOPY")
Signed-off-by: Michal Luczaj <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

net/vmw_vsock/af_vsock.c

···
 		} else {
 			newsock->state = SS_CONNECTED;
 			sock_graft(connected, newsock);
+
+			set_bit(SOCK_CUSTOM_SOCKOPT,
+				&connected->sk_socket->flags);
+
 			if (vsock_msgzerocopy_allow(vconnected->transport))
 				set_bit(SOCK_SUPPORT_ZC,
 					&connected->sk_socket->flags);