target/loongarch: Add loongarch kvm into meson build

target/loongarch: Add loongarch kvm into meson build

Add kvm.c into meson.build to compile it when kvm
is configed. Meanwhile in meson.build, we set the
kvm_targets to loongarch64-softmmu when the cpu is
loongarch. And fix the compiling error when config
is enable-kvm,disable-tcg.

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: <20240105075804.1228596-10-zhaotianrui@loongson.cn>
Signed-off-by: Song Gao <gaosong@loongson.cn>