target/loongarch: Implement kvm_arch_init_vcpu

target/loongarch: Implement kvm_arch_init_vcpu

Implement kvm_arch_init_vcpu interface for loongarch,
in this function, we register VM change state handler.
And when VM state changes to running, the counter value
should be put into kvm to keep consistent with kvm,
and when state change to stop, counter value should be
refreshed from kvm.

Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: xianglai li <lixianglai@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20240105075804.1228596-7-zhaotianrui@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>