nios2: remove empty files from nios2e-zephyr 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 empty files that don't do anything. Change-Id: I4214d21104fe5f49613fa5697c8116b0e8c8aa50 Signed-off-by: Kumar Gala <kumar.gala@linaro.org>