Move the board specific configurations into its own header file, which
can now be created per board, once it gets tested and validated by the
bootloader.
Signed-off-by: Ricardo Salveti <ricardo.salveti@linaro.org>
The Zephyr build system does strange things if it refers to source
directories above the main Makefile (generating
outdir/<target>/../boot/... paths). For now, fix this by moving the
Zephyr Makefile to the top-level in the tree. This shouldn't have much
impact on Mynewt, as it doesn't use makefiles.