platform: Add T-head C910 initial support

This commit provides basic support for the Thead/C910 platform.

Signed-off-by: Liu Yibin <yibin_liu@c-sky.com>
Reviewed-by: Atish Patra <atish.patra@wdc.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>