board/km: update MAINTAINERS files

Update the e-mail addresses and person responsible.

Signed-off-by: Holger Brunck <holger.brunck@hitachienergy.com>
CC: Aleksandar Gerasimovski <aleksandar.gerasimovski@hitachienergy.com>
CC: Rainer Boschung <rainer.boschung@hitachienergy.com>
diff --git a/board/keymile/km_arm/MAINTAINERS b/board/keymile/km_arm/MAINTAINERS
index 8da58da..bc6858b 100644
--- a/board/keymile/km_arm/MAINTAINERS
+++ b/board/keymile/km_arm/MAINTAINERS
@@ -1,5 +1,5 @@
 KM_ARM BOARD
-M:	Valentin Longchamp <valentin.longchamp@hitachi-powergrids.com>
+M:	Holger Brunck <holger.brunck@hitachienergy.com>
 S:	Maintained
 F:	board/keymile/km_arm/
 F:	include/configs/km_kirkwood.h