target/loongarch: Move kvm specified vCPU property to kvm directory LBT and PMU feature is supported only in kvm mode, move property about these two features to function kvm_loongarch_cpu_post_init(). Signed-off-by: Bibo Mao <maobibo@loongson.cn> Reviewed-by: Bibo Mao <maobibo@loongson.cn>