linux-libc-headers-yocto: disable device tree generation
Fixes [BUGID #719]
The common routines for handling a git based yocto kernel
are included from the lib headers recipe to checkout the
appropriate branch of the kernel for header generation.
linux-yocto.inc includes device tree installation rules
which typically apply to a kernel user of the include file,
but do not apply to a simple header generation. The fix is
to override the DTB variables in this recipe, which disable
the device tree installation rules.
Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
