chromeos-google-touch-firmware-update-legacy.sh: EOL flashrom usage for WP

The flashrom/cros_ec driver is EOL. As part of its removal
the TP subtype is being dropped. Trivially replace the WP
status query with that of ectool instead.

BUG=b:262782150,b:282855423
TEST=On eve with TP write protect enabled,
call `ectool --name=cros_tp flashprotect` and get:
Flash protect flags: 0x0000000f wp_gpio_asserted ro_at_boot \
ro_now all_now
Valid flags:         0x0000003f wp_gpio_asserted ro_at_boot \
ro_now all_now STUCK INCONSISTENT
Writable flags:      0x00000000
TEST=Parse the above message with `sed`

Change-Id: I7786112f493ffcbc1ad9662e8b6ea51fc3cf17ee
Signed-off-by: Edward O'Callaghan <quasisec@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/touch_updater/+/4736872
Reviewed-by: Edward O'Callaghan <quasisec@chromium.org>
Tested-by: Hsuan Ting Chen <roccochen@chromium.org>
Commit-Queue: Hsuan Ting Chen <roccochen@chromium.org>
Auto-Submit: Edward O'Callaghan <quasisec@chromium.org>
Reviewed-by: Henry Barnor <hbarnor@chromium.org>
Reviewed-by: Peter Marheine <pmarheine@chromium.org>
1 file changed