14.5.1

workflows/assets.yml: Change release assets

This commit changes the assets workflow to:

1. Produce assets for arm64 platform variants: nvidia-jp5 and nvidia-jp6
2. Fix the assets for IPXE installer
3. Create a sha256sum for all files

Signed-off-by: Renê de Souza Pinto <rene@renesp.com.br>