platform: thead/c910: Use HSM extension to boot secondary cores

Remove custom vendor extension and use HSM extension
to boot secondary cores

Signed-off-by: Liu Yibin <yibin_liu@c-sky.com>
Reviewed-by: Anup Patel <anup.patel@wdc.com>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>