All ubuntu_kvm_unit_tests sub-tests failed on P8 node dryden with Hirsute and newer

Issue found on Impish 5.13.0-24.24 with P8 node dryden (passed on P9 node baltar, P8 node entei), this issue can be reproduced on Hirsute as well.

After the kvm-unit-tests build issue fixed on PowerPC (bug 1931534), it can be tested on PowerPC. However all 8 sub-tests on node dryden failed with:
  qemu-system-ppc64: Requested count cache flush assist capability level not supported by KVM

Failed tests:
  * emulator
  * h_cede_tm
  * rtas-get-time-of-day
  * rtas-get-time-of-day-base
  * rtas-set-time-of-day
  * selftest-setup
  * spapr_hcall
  * sprs

One of the failure:
 Running 'ppc64_cpu --smt=off'
 Running '/home/ubuntu/autotest/client/tmp/ubuntu_kvm_unit_tests/src/kvm-unit-tests/tests/rtas-set-time-of-day'
 BUILD_HEAD=16647354
 timeout -k 1s --foreground 5 /usr/bin/qemu-system-ppc64 -nodefaults -machine pseries,accel=kvm -bios /tmp/tmp.hze7twEXSz -display none -serial stdio -kernel /tmp/tmp.IOczCobdEm -smp 1 -append set-time-of-day # -initrd /tmp/tmp.ybMdG1FZhO
 qemu-system-ppc64: Requested count cache flush assist capability level not supported by KVM
 Try appending -machine cap-ccf-assist=off
 FAIL rtas-set-time-of-day