Android: fix L and R buttons

Fixes Issue 7144.

The L and R buttons did not work on Android. Turns out in one of the source files they were set as axises instead of buttons, and they were also mapped incorrectly. This does not fix L and R triggers that are mapped to physical buttons, but it does fix the on-screen buttons. I may look into the physical buttons later, but for now we can at least have one way of using the triggers.