forked from Mirrors/opensbi

Init of non-standard extensions is a platform-specific thing, so allow generic platforms to do this via a platform-override. Reviewed-by: Andrew Jones <ajones@ventanamicro.com> Reviewed-by: Guo Ren <guoren@kernel.org> Reviewed-by: Anup Patel <anup@brainfault.org> Signed-off-by: Heiko Stuebner <heiko@sntech.de>