ARM: microsom: change barebox image name for Hummingboard
To reflect that the current image is in fact for a combination of a
MicroSOM i1 with a Hummingboard baseboard.
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>