devtmpfs: fix placement of complete() call

Calling complete() from within the __init function is wrong -
theoretically, the init process could proceed all the way to freeing
the init mem before the devtmpfsd thread gets to execute the return
instruction in devtmpfs_setup().

In practice, it seems to be harmless as gcc inlines devtmpfs_setup()
into devtmpfsd(). So the calls of the __init functions init_chdir()
etc. actually happen from devtmpfs_setup(), but the __ref on that one
silences modpost (it's all right, because those calls happen before
the complete()). But it does make the __init annotation of the setup
function moot, which we'll fix in a subsequent patch.

Fixes: bcbacc49 ("devtmpfs: refactor devtmpfsd()")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Link: https://lore.kernel.org/r/20210312103027.2701413-1-linux@rasmusvillemoes.dkSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/base/devtmpfs.c

@@ -419,7 +419,6 @@ static int __init devtmpfs_setup(void *p)
 	init_chroot(".");
 out:
 	*(int *)p = err;
-	complete(&setup_done);
 	return err;
 }
 
@@ -432,6 +431,7 @@ static int __ref devtmpfsd(void *p)
 {
 	int err = devtmpfs_setup(p);
 
+	complete(&setup_done);
 	if (err)
 		return err;
 	devtmpfs_work_loop();