KVM: arm64: Unregister perf callbacks if hypervisor finalization fails

Undo everything done by init_subsystems() if a later initialization step
fails, i.e. unregister perf callbacks in addition to unregistering the
power management notifier.

Fixes: bfa79a80 ("KVM: arm64: Elevate hypervisor mappings creation at EL2")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20221130230934.1014142-19-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>