target/alpha: Use generic cpu_list()

target/alpha: Use generic cpu_list()

Before it's applied:

[gshan@gshan q]$ ./build/qemu-system-alpha -cpu ?
Available CPUs:
  ev4-alpha-cpu
  ev5-alpha-cpu
  ev56-alpha-cpu
  ev6-alpha-cpu
  ev67-alpha-cpu
  ev68-alpha-cpu
  pca56-alpha-cpu

After it's applied:

[gshan@gshan q]$ ./build/qemu-system-alpha -cpu ?
Available CPUs:
  ev4
  ev5
  ev56
  ev6
  ev67
  ev68
  pca56

Signed-off-by: Gavin Shan <gshan@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Message-ID: <20231114235628.534334-8-gshan@redhat.com>
Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>