Fixes [BUGID #610]
The powerpc linux-yocto kernels were not creating dtb images
in the deploy directories. This was due to two problems:
- the dtb generation rules were not being configured
- the boards were not specifying a device tree in their config
This change addresses the first point by factoring out the
dtb generation routines into a new include that can be used by
multiple recipes.
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>