This was the intention since the beginning (based on images built by
Google. Clean up code and mark the platform associated with GCE image
types as UEFI-only.
The only missing part is the default partition table used by the GCE
image, which is shared with other image types and still contains the
BIOS boot partition. I added a TODO comment to preserve this
information, but kept things as they are for now to not have to
introduce a new set of GCE-specific base partition tables.
Signed-off-by: Tomáš Hozza <thozza@redhat.com>
2c686cc988