DIOM3 is no longer used. Remove it from gpio.inc
BUG=chrome-os-partner:55895,chrome-os-partner:55896
BRANCH=none
TEST=make buildall; test on Cr50 hardware
Change-Id: I1f7aeab8135fa97aab04945b6a450e32903e2e84
Signed-off-by: Bill Richardson <wfrichar@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/372405
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>