host/lib/flashrom_drv.c: Move flag to avoid locked ME issue

Older Intel DUT's have a ME in "locked" mode in the descriptor
and while the write_flash() attempts to write back to flash
to a specific region it needs to read the FMAP to obtain the
region name. This read overlaps with the "locked" region and
thus the following is observed in logs:

```
FREG2: Management Engine region (0x00001000-0x001fffff) is locked.
[..]
read_flash: cannot read inside Management Engine region (0x001000..0x1fffff).
```

BUG=b:269199980
TEST=builds.

Change-Id: If7bebf28cd4d34cc4074700184233c83edbd2409
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/vboot_reference/+/4248344
Auto-Submit: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Sam McNally <sammc@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Tested-by: Edward O'Callaghan <quasisec@chromium.org>
Commit-Queue: Edward O'Callaghan <quasisec@chromium.org>