There is no easy way to disable that with an Android device. Supposedly, the android system needs to see a small amount of voltage on that port to "enable it" .
There are modified cables or root of the device but not worth the effort.
You will have no trouble flying through at least 4-5 batteries/flights (normal time of use unless doing surveying, etc) before you have to worry about the controller's battery level.
If using the controller for much longer than that, you could connect a portable USB power bank to the bottom charging port while flying to have the controller charging as well.
If I am using my phone or tablet with the standard controller for any length of time (I primarily use the
Smart Controller) I set them to disable "fast charging" to keep that charging to a minimum and cut down on the heat caused when charging.