updater: Preserve SI_GBE and SI_PDR if present
updater: Preserve SI_GBE and SI_PDR if present

On a full firmware update we need to preserve these regions:

SI_GBE contains the unique MAC address for the system
SI_PDR contains data from the factory and diagnostics

BUG=b:126637087
BRANCH=none
TEST=futility update image-sarien.bin

Change-Id: I2981c8cc478617029934ef3fbdb1c446c858fad8
Signed-off-by: Duncan Laurie <70662b43bc1a20b57ded72a2b08be88dd0da4841@google.com>
Reviewed-on: https://chromium-review.googlesource.com/1493629
Commit-Ready: ChromeOS CL Exonerator Bot <fa429e5907f00867f797423aea74327bb02c91b6@appspot.gserviceaccount.com>
Reviewed-by: Hung-Te Lin <8a7fce4940baad93a69f5073b383c85deed9d9c4@chromium.org>

coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot,coreboot/vboot