target/loongarch/kvm: Include missing exec/target_long.h header

After commit 71cab1a42d2 removed the indirect include of exec/cpu-defs.h from target/loongarch/cpu.h, the TARGET_FMT_lx macro is no longer visible in kvm.c, causing build failures: error: expected ')' before TARGET_FMT_lx Add the missing exec/target_long.h to fix it. Cc: qemu-stable@nongnu.org Fixes: 71cab1a42d2 ("target/cpu: Do not include 'exec/cpu-defs.h' anymore") Signed-off-by: Qiang Ma <maqianga@uniontech.com> Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org> Reviewed-by: Song Gao <gaosong@loongson.cn> Message-ID: <20260601014601.4047201-1-gaosong@loongson.cn> Signed-off-by: Song Gao <gaosong@loongson.cn>