Safer ABI for O_TMPFILE

[suggested by Rasmus Villemoes] make O_DIRECTORY | O_RDWR part of O_TMPFILE;
that will fail on old kernels in a lot more cases than what I came up with.
And make sure O_CREAT doesn't get there...

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namei.c b/fs/namei.c
index b2beee7..8b61d10 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -2977,7 +2977,7 @@
 
 	file->f_flags = op->open_flag;
 
-	if (unlikely(file->f_flags & O_TMPFILE)) {
+	if (unlikely(file->f_flags & __O_TMPFILE)) {
 		error = do_tmpfile(dfd, pathname, nd, flags, op, file, &opened);
 		goto out;
 	}