vboot_reference/Makefile: Work towards a common flashrom path

There are multiple flashrom calling wrapping code implementations
within vboot_ref. Work towards making a singular canonical
implementation.

BUG=b:207808292
BRANCH=none
TEST=`make`

Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Change-Id: I8e133a11b777b4e80bb4e43a64a5349956cef8eb
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/3325329
Tested-by: Edward O'Callaghan <quasisec@chromium.org>
Auto-Submit: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Nikolai Artemiev <nartemiev@google.com>
Commit-Queue: Edward O'Callaghan <quasisec@chromium.org>
1 file changed