target/loongarch: Implement kvm_arch_handle_exit

target/loongarch: Implement kvm_arch_handle_exit

Implement kvm_arch_handle_exit for loongarch. In this
function, the KVM_EXIT_LOONGARCH_IOCSR is handled,
we read or write the iocsr address space by the addr,
length and is_write argument in kvm_run.

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: <20240105075804.1228596-8-zhaotianrui@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>