target/loongarch: Implement kvm get/set registers

target/loongarch: Implement kvm get/set registers

Implement kvm_arch_get/set_registers interfaces, many regs
can be get/set in the function, such as core regs, csr regs,
fpu regs, mp state, etc.

Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: xianglai li <lixianglai@loongson.cn>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Change-Id: Ia8fc48fe08b1768853f7729e77d37cdf270031e4
Message-Id: <20240105075804.1228596-5-zhaotianrui@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>