MIPS: Loogson: Make enum loongson_cpu_type more clear

MIPS: Loogson: Make enum loongson_cpu_type more clear

Sort enum loongson_cpu_type in a more reasonable manner, this makes the
CPU names more clear and extensible. Those already defined enum values
are renamed to Legacy_* for compatibility.

Signed-off-by: Huacai Chen <chenhc@lemote.com>
Cc: John Crispin <john@phrozen.org>
Cc: Steven J . Hill <Steven.Hill@cavium.com>
Cc: Fuxin Zhang <zhangfx@lemote.com>
Cc: Zhangjin Wu <wuzhangjin@gmail.com>
Cc: linux-mips@linux-mips.org
Patchwork: https://patchwork.linux-mips.org/patch/16591/
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>