This allows platforms that don't have libpci to configure the code
without error.

BUG=560948

Change-Id: I155f35108d9be193afed5304b443a6afdf33b077
Reviewed-on: https://chromium-review.googlesource.com/314300Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>
Tested-by: Stephen Mcgruer <smcgruer@google.com>
Tested-by: Jamie Madill <jmadill@chromium.org>