Bluetooth: AT: Unit: Fixup include search path

Because of the way we build we can't expect relative paths back into the
Zephyr code base to work properlly.  This just happens to work on some
systems because of the various -I that exist and one hits the right
number of subdirs between it and where the "at.h" lives.  Lets instead
add the Zephyr root as a include path and explicit do a relative path
from the root to get the header.

We end up with a build failure with newlib enabled on galileo because it
ends up not having an include path that gets us to the proper spot with
the various ../../.. ...

Change-Id: I48b4dc2dffb76314f380efbcbbe25957ff5e9e07
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>
2 files changed