google_chromeec_get_event returns 0 for no event. Return EC_HOST_EVENT_NONE=0 to improve readability. BUG=b:184074997 TEST=Build and boot guybrush without error Signed-off-by: Rob Barnes <robbarnes@google.com> Change-Id: Ic08ed9ccdd7c0023d0fe8b641fcf60dca495a242 Reviewed-on: https://review.coreboot.org/c/coreboot/+/55547 Tested-by: build bot (Jenkins) <no-reply@coreboot.org> Reviewed-by: Tim Wawrzynczak <twawrzynczak@chromium.org>