KVM selftests for 6.11
- Remove dead code in the memslot modification stress test.
- Treat "branch instructions retired" as supported on all AMD Family 17h+ CPUs.
- Print the guest pseudo-RNG seed only when it changes, to avoid spamming the
log for tests that create lots of VMs.
- Make the PMU counters test less flaky when counting LLC cache misses by
doing CLFLUSH{OPT} in every loop iteration.