basesdk,sdk: Install packages needed by signed kernel support

The previous commits added the initial bits for trusted boot on i.MX6 boards using signed FIT images for kernel+initramfs.

This commit adds the new dependencies to genereate the FIT image and sign them in a way compatible with the High Assurance Boot (HAB) system for i.MX6, as our image reciepes should work out of the box on the SDK images.

See https://lava.collabora.co.uk/scheduler/job/2243455 for the failing testcase and https://lava.collabora.co.uk/scheduler/job/2243509 for one where the needed dependencies got installed: it still fails, but only because it can't find the key in the right place.