target/loongarch: Define some kvm_arch interfaces

target/loongarch: Define some kvm_arch interfaces

Define some functions in target/loongarch/kvm/kvm.c,
such as kvm_arch_put_registers, kvm_arch_get_registers
and kvm_arch_handle_exit, etc. which are needed by
kvm/kvm-all.c. Now the most functions has no content
and they will be implemented in the next patches.

Signed-off-by: Tianrui Zhao <zhaotianrui@loongson.cn>
Signed-off-by: xianglai li <lixianglai@loongson.cn>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Song Gao <gaosong@loongson.cn>
Message-Id: <20240105075804.1228596-3-zhaotianrui@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>