quark_se_sss_devboard: Remove empty board file

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: I6e5ce35bd7b9b4411820bc112a08dd0d809495d6
Signed-off-by: Kumar Gala <kumar.gala@linaro.org>