zenfone6: override fstab.qcom from vendor to remove wrappedkey

* Asus has `wrappedkey` enabled in their fstab but actually does not
use it at all. To match this, we have to override the fstab by
bind-mounting.
diff --git a/device.mk b/device.mk
index 849efe9..a015c92 100755
--- a/device.mk
+++ b/device.mk
@@ -118,6 +118,10 @@
 PRODUCT_AAPT_CONFIG := xxhdpi
 PRODUCT_AAPT_PREF_CONFIG := xxhdpi
 
+# Rootdir
+PRODUCT_COPY_FILES += \
+    $(LOCAL_PATH)/recovery.fstab:system/etc/fstab.qcom
+
 # Netutils
 PRODUCT_PACKAGES += \
     netutils-wrapper-1.0 \