Verify that disabling the guest's vPMU via CPUID also disables LBRs.
KVM has had at least one bug where LBRs would remain enabled even though
the intent was to disable everything PMU related.
Link: https://lore.kernel.org/r/20230311004618.920745-22-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>