Instead of having a generic "virt_qemu" board use "virt_qemu_<arch>" in
order to have a clean distinction between boards. Current supported
boards are "virt_qemu_arm_v7a", "virt_qemu_arm_v8a", and
"virt_qemu_riscv".
issue #4034
The 'aes_cbc_4k' library is simple wrapper around libsparkcrypto to
serve as a backend for storage encryption. It operates on data chunks of
4 KiB and uses AES-CBC while incorporating the block number and the
private key as salt values.
