forked from Mirrors/opensbi

As of today all platforms use 8KB of per-HART stack hence there is no need for each platform to define its own macro or use the magic number. Create one macro for all platforms. Platform still can use its own version if needed. Signed-off-by: Bin Meng <bmeng.cn@gmail.com> Reviewed-by: Anup Patel <anup.patel@wdc.com>