OpenStack boot regressions caused by "ppc64: Restrict memory allocations for kernel and initrd"

[Mate Kukri]

Hello,

We have discovered a boot regression on virtual machines in
Canonical's OpenStack cloud when upgrading from 2.12-rc1 to 2.12 on
ppc64.

It was tracked down to the following patchset:
https://lists.gnu.org/archive/html/grub-devel/2023-11/msg00188.html

The boot regressions seem to be related to GRUB running out of memory
when loading initrds:
https://objectstorage.prodstack5.canonical.com/swift/v1/AUTH_0f9aae918d5b4744bf7b827671c86842/autopkgtest-noble/noble/ppc64el/z/zsys/20240213_214024_bf6af@/log.gz

As a temporary solution, I have reverted the patchset in Ubuntu, but I
wonder if anything else is effected by this.

Mate Kukri