Harts with id greater than or equal to CONFIG_NR_CPUS need to be
disabled.  But the kernel can pick any hart as the main hart.  So,
before picking the main hart, the kernel must disable harts with ids
greater than or equal to CONFIG_NR_CPUS.
Signed-off-by: NXiang Wang <merle@hardenedlinux.org>
Reviewed-by: NPalmer Dabbelt <palmer@sifive.com>
Reviewed-by: NAnup Patel <anup.patel@wdc.com>
[paul.walmsley@sifive.com: updated to apply; cleaned up patch
 description]
Signed-off-by: NPaul Walmsley <paul.walmsley@sifive.com>