GRUB_IEEE1275_FLAG_NO_TREE_SCANNING_FOR_DISKS is set.
* grub-core/kern/ieee1275/cmain.c (grub_ieee1275_find_options): Set
GRUB_IEEE1275_FLAG_NO_TREE_SCANNING_FOR_DISKS on IBM hardware.
* include/grub/ieee1275/ieee1275.h (grub_ieee1275_flag): New enum value
GRUB_IEEE1275_FLAG_NO_TREE_SCANNING_FOR_DISKS.