net: clear msg_get_inq in __get_compat_msghdr()

syzbot is still complaining uninit-value in tcp_recvmsg(), for
commit 1228b34 ("net: clear msg_get_inq in __sys_recvfrom() and
__copy_msghdr_from_user()") missed that __get_compat_msghdr() is called
instead of copy_msghdr_from_user() when MSG_CMSG_COMPAT is specified.

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Fixes: 1228b34 ("net: clear msg_get_inq in __sys_recvfrom() and __copy_msghdr_from_user()")
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/d06d0f7f-696c-83b4-b2d5-70b5f2730a37@I-love.SAKURA.ne.jp
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/compat.c

@@ -52,6 +52,7 @@ int __get_compat_msghdr(struct msghdr *kmsg,
 		kmsg->msg_namelen = sizeof(struct sockaddr_storage);
 
 	kmsg->msg_control_is_user = true;
+	kmsg->msg_get_inq = 0;
 	kmsg->msg_control_user = compat_ptr(msg->msg_control);
 	kmsg->msg_controllen = msg->msg_controllen;