This also change the beaglebone target to use a GPT
partitioned disk
BREAKING CHANGE: .swu image generated can not be used on old
device, thus the device has to be reflashed.
BREAKING CHANGE: Support for MBR formatted disk is removed, as
it was only used for Beaglebone
--fixed-size produce a partition of the right size but doesn't expand
the filesystem. Instead we use --size --extra-space and
--overhead-factor to have a fixed size partition and fixed size
filesystem
We are now using efibootguard to provide a A/B boot path for
the kernel and the rootfs.
This commit remove some change for systemd/systemd-boot that are
not needed anymore and rework how we set the command line, as we
will need to have the command line argument of the kernel both
inside do_image_wic and in a future do_image_swu
Peter Kindler
Samuel Dolt