1. Sign in using your PSN account
2. Click on the Account tab
3. On the left, select Media & Devices
4. On the four options that show up, click on GAME
5. Deactivate All
6. You are about to deactivate all devices on your account for game media.
- This action can be performed only once every 6 months.
- To play games that were previously downloaded, you will need to activate a device from the [Account Management] menu on the device.
That's all you can do at the moment until Playstation releases their new page that allows you to deactivate one single system.