This ports the following barebox commit:

| commit ec01cbc
| Author: Ian Abbott <abbotti@mev.co.uk>
| Date:   Fri Apr 21 10:53:25 2017 +0100
|
|     state: Fix "pack" returning freed data for DTB backend
|
|     `state_backend_format_dtb_pack()` passes a buffer containing state
|     packed in flattened DTB format back to its caller via its `buf`
|     parameter.  It then frees the buffer before returning.  This means the
|     caller (`state_save()`) will be working on freed buffer contents before
|     freeing the buffer a second time itself.  Fix it by removing the
|     spurious call to `free()`.
|
|     This should fix a bug reported by Norbert Wiedmann in
|     <http://lists.infradead.org/pipermail/barebox/2017-April/029980.html>.
|
|     Cc: Norbert Wiedmann <info@n-wiedmann.de>
|     Signed-off-by: Ian Abbott <abbotti@mev.co.uk>
|     Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

Signed-off-by: Ulrich Ölmann <u.oelmann@pengutronix.de>
Signed-off-by: Roland Hieber <rhi@pengutronix.de>