crossystem: Return error when trying to read GPIO port zero

For the record, zero is a valid GPIO port number.  Unfortunately
firmware uses port zero to denote that a GPIO port is not exist.
So crossystem should not attempt to read GPIO port zero, but
return error instead.

Signed-off-by: Che-Liang Chiou <clchiou@chromium.org>

BUG=chrome-os-partner:11296
TEST=On Snow, run crossystem and see devsw_cur and recoverysw_cur
     are "(error)"

Change-Id: I70b15824f613df1e46bf152515ad4e9362c9f066
Reviewed-on: https://gerrit.chromium.org/gerrit/27251
Commit-Ready: Che-Liang Chiou <clchiou@chromium.org>
Tested-by: Che-Liang Chiou <clchiou@chromium.org>
Reviewed-by: Cheng-Yi Chiang <cychiang@chromium.org>
Tested-by: Cheng-Yi Chiang <cychiang@chromium.org>
1 file changed