Use a kbuild trick to force built-in.o to get built even if there isn't
any code so we can link properly. This is cleaner than keeping around
files that don't do anything.
We keep around board.h for now since drivers and other code might expect
it to exist.
Change-Id: Ia55a2614d3eea1920f1be7880be2bf82c6c3c7db
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>