embedded-a/corstone1000: Add secureboot testing script
This changeset adds the secureboot testing script. This script is responsible to create the secureboot UEFI authenticated variables, sign the kernel images for both Corstone-1000 FVP and FPGA with these authenticated variables, and copy the keys, signed and unsigned kernel images to the ESP images for both the FVP and FPGA.
Signed-off-by: Harsimran Singh Tungal harsimransingh.tungal@arm.com