Using an Alpha 8 image as an alpha mask on Android 6.X devices with Mali GPU the mask doesn't work (the mask isn't masking) when built with GLES 3.0 or 3.1 graphics API.

Reproduction steps:
1. Open the attached project (788821-ReproProject.zip)
2. Open and play the "test" scene
3. Notice that the image is masked (check Nexus5.jpg)
4. Build and run the project on Android 6.X device with Mali GPU targeting GLES 3.0 or 3.1 graphics API
5. Notice that the image isn't masked (check Note4.png)