target/loongarch: Use generic cpu_list()

target/loongarch: Use generic cpu_list()

Before it's applied:

[gshan@gshan q]$ ./build/qemu-system-loongarch64 -cpu ?
la132-loongarch-cpu
la464-loongarch-cpu
max-loongarch-cpu

After it's applied:

[gshan@gshan q]$ ./build/qemu-system-loongarch64 -cpu ?
Available CPUs:
  la132
  la464
  max

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Message-ID: <20231114235628.534334-14-gshan@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>