target/loongarch: Restrict TCG-specific code

target/loongarch: Restrict TCG-specific code

In preparation of supporting KVM in the next commit.

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: <20240105075804.1228596-9-zhaotianrui@loongson.cn>
[PMD: Split from bigger patch, part 1]
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-Id: <20240110094152.52138-1-philmd@linaro.org>
Signed-off-by: Song Gao <gaosong@loongson.cn>