This change improves EFI boot support when presented with multiple valid boot partitions across multiple devices.
It now prefers to boot from partitions that are present on the underlying device that the boot1 image was loaded from.
This means that it will boot from the partitions on device the user chose from EFI boot menu in preference to those on other devices.
Also fixed is the recovery from a failed attempt to boot, from a seeming valid partition, by continuing to trying all other available partitions no matter what the error.
Finally some error messages where improved and DPRINTF's added to aid failure debugging.
boot1 now use * to signify a partition what was accepted from the preferred device and + otherwise.
ZFS will still be preferred over UFS when available.