simplify MLO/UBOOT board table
simplify MLO/UBOOT board table

Signed-off-by: Robert Nelson <d6c41255011d14bfa93d8562b946ca186cfa0c7b@gmail.com>

jadonk/image-builder,RobertCNelson/omap-image-builder,mhaberler/omap-image-builder,miloh/image-builder,beagleboard/image-builder,miloh/image-builder,eliasbakken/kamikaze,beagleboard/image-builder,robert-budde/omap-image-builder,jadonk/image-builder,hankchan/bbb-image-builder,RobertCNelson/omap-image-builder,gthrive/image-builder,jlefley/omap-image-builder,robert-budde/omap-image-builder,eliasbakken/omap-image-builder,OpenROV-forks/omap-image-builder,OpenROV-forks/omap-image-builder,BrianAdams/omap-image-builder