mb/google/guybrush: Add signed verstage

Add signed verstage for Nipperkin and Guybrush based on FW: 14283.0.0

BUG=b:201547951
TEST=Build and boot to OS in Guybrush and Nipperkin.

Change-Id: I25ff08f4fa05adc02dbb56a8fb035f248b5f6ff4
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/coreboot/blobs/+/3235589
Tested-by: Karthikeyan Ramasubramanian <kramasub@chromium.org>
Reviewed-by: Raul E Rangel <rrangel@chromium.org>
Commit-Queue: Karthikeyan Ramasubramanian <kramasub@chromium.org>
3 files changed