vboot_ref/futility: Wrap flashrom_drv behind USE_FLASHROM

Some users of futility do not need flashrom support such
as upstream coreboot. Allow for explicitly enabling the
paths.

BUG=b:203715651,b:209702505
BRANCH=none
TEST=builds

Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Change-Id: I61095bf91e3d01bd008d3b790478a590758e88cd
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3350299
Tested-by: Edward O'Callaghan <quasisec@chromium.org>
Auto-Submit: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Yu-Ping Wu <yupingso@chromium.org>
Reviewed-by: Hsuan Ting Chen <roccochen@chromium.org>
Commit-Queue: Hsuan Ting Chen <roccochen@chromium.org>
2 files changed