Prevent mount-fix from being upgraded

- Prevent the mount-fix package from being upgraded.

ipk-source/sdxpinn-mount-fix/CONTROL/preinst

@@ -1,5 +1,11 @@
 #!/bin/ash
 
+if grep -qs '/real_rootfs' /proc/mounts; then
+    echo "This package is meant to be installed once after a clean flash."
+    echo "You should not upgrade or reinstall it. Flash first then run the toolkit otherwise."
+    exit 1
+fi
+
 # Remount original rootfs as read-write 
 echo "Mounting / as read-write"
 mount -o remount,rw /