I ran into a build failure with --enable-targets=all due to the fact that
the moxie sim expects to be able to use the dtc tool. If it isn't available,
the builds fails.
The following patch adds a prebuilt dtb file to the tree. That file is the one
that is used for installations.
The patch also enables (re-)generation of the dtb file through maintainer
mode, if it needs to be updated due to a change in the dts file.