futility: cmd_update: Use real system write protection status
futility: cmd_update: Use real system write protection status

The updater logic is heavily based on write protection status. The write
protection must be decided by two sources: hardware ("write protection
switch", known as `wpsw` in crossystem) and software (on most SPI, this
is controlled by SRP0 register using flashrom).

When debugging firmware updating issues, it is very important to have
complete logs for status of all WP sources (hw and sw, and the final
decision by updater itself - maybe overridden by --wp).

This change tries to handle WP properly and also leaving enough
information of how the WP logic was decided.

BUG=chromium:875551
TEST=make futil; tests/futility/run_test_scripts.sh $(pwd)/build/futility
BRANCH=None

Change-Id: I15dc2dbcefc421c1194aa623e15f00d793653e93
Signed-off-by: Hung-Te Lin <8a7fce4940baad93a69f5073b383c85deed9d9c4@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1183658
Reviewed-by: Randall Spangler <62698fdbb84d1779579ee80c3f39fac22017e5bc@chromium.org>

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