Add 2nd cryptdevice for chaining encrypted disks

[allhavebrainimplantsandmore]

In Archlinux you can add hooks to mkinitcpio to create more cryptdevices for Grub2 to use during boot. That way you can nest encrypted devices and boot rootfs from a nested encrypted device pretty easily. Not seeing this possible in dracut at this time. Maybe also add ability to use plain dm-crypt devices instead of hardcoding Luks encrypted partitions.