MFV r289526:
5561 support root pools on EFI/GPT partitioned disks
5125 update zpool/libzfs to manage bootable whole disk pools (EFI/GPT labeled disks)

Reviewed by: Jean McCormack <jean.mccormack@nexenta.com>
Reviewed by: Josef 'Jeff' Sipek <josef.sipek@nexenta.com>
Approved by: Dan McDonald <danmcd@omniti.com>
Author: Hans Rosenfeld <hans.rosenfeld@nexenta.com>

illumos/illumos-gate@1a902ef8628b0dffd6df5442354ab59bb8530962

This is NOP changes for FreeBSD.