Support systemlessly deleting files or folders

After we refactor the magic mount and always mount folder as tmpfs,
we can easily support deleting files or folders now. We recognize
dummy devices with major number 0 and minor number 0 as an indicator
for removing files and folders. This indicator is borrowed from
overlayfs.

scripts/util_functions.sh

@@ -702,6 +702,11 @@ install_module() {
     mktouch $MODPATH$TARGET/.replace
   done
 
+  for TARGET in $REMOVE; do
+    ui_print "- Remove target: $TARGET"
+    mknod $MODPATH$TARGET c 0 0
+  done
+
   if $BOOTMODE; then
     # Update info for Magisk app
     mktouch /data/adb/modules/$MODID/update