!792 LoongArch: add ls2k500 bmc support

Merge Pull Request from: @Hongchen_Zhang 
 
Add ls2k500 bmc support:
- add ls2k500sfb driver for ls2k500 bmc
- add ls2k500 bmc ipmi support
- enable CONFIG_FB_LS2K500 by default 
 
Link:https://gitee.com/openeuler/kernel/pulls/792

 

Reviewed-by: Guo Dongtai <guodongtai@kylinos.cn>
Reviewed-by: Jialin Zhang <zhangjialin11@huawei.com>
Signed-off-by: Jialin Zhang <zhangjialin11@huawei.com>