This ports the following barebox commit:

| commit 8db7a23
| Author: Juergen Borleis <jbe@pengutronix.de>
| Date:   Wed Aug 16 14:27:07 2017 +0200
|
|     state: provide an error message when an error occurs
|
|     A simple typo makes the state framework fail, but without an error
|     message the developer is lost in the dark.
|
|     Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
|     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>