set console=hvc0 via boot option. This configuration make init to add
hvc0 to /etc/inittab and /etc/securetty. This is needed to allow login
with 'root' user.
To boot ppc64le we need to use grub with ieee1275 platform. Said that,
a new section to support grub ieee1275 was created.
Also needed to change xorrisofs command by grub-mkrescue, that is the one
used to create a bootable image for power and it is also a wrapper to xorriso.
not enabled yet, but uncommenting the grub_mod should enable
building of isolinux+grubefi hybrid images. once uefi boot works
and is verified on aarch64, we can enable the vanilla iso image
(grsec does not support aarch64).
the boot repositry needs to be signed with a key. We explicitly copy
this to initramfs so users don't need use --hostkeys which requires
access to /etc/apk/keys/
without the key in intramfs the boot repository will be useless
