Only allow eng load built in emimpu sysfs. MTK-Commit-Id: d43a97a0d48e41ba361ea94cd9f392ca2a179c58 Change-Id: I37e409faee83bf480e9b6d15be46d18737d81611 Signed-off-by: mtk21827 <joanne.wang@mediatek.com> CR-Id: ALPS05377669 Feature: External Memory Interface(emi)