kernel upgrade on ppc64le-db-bbw1

To avoid frequent test failures: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1032104

Can we do one of the following:

• install a RHEL distribution (known not to have problems)
• Install SUSE distro (though licences still a problem)
• update to Ubuntu 22.04 (4 more years of support)
• try a Debian backports kernel - https://packages.debian.org/bullseye-backports/linux-image-5.19.0-0.deb11.2-powerpc64le (with 1 more year left of Debian 11 support)