Fix off by one bug with GetGamepadAxisCount on PLATFORM_DESKTOP (#1715)

- Found testing core_input_gamepad. The last axis was not drawn.
- GLFW_GAMEPAD_AXIS_LAST is defined to the last axis which is 5
not the total number which is 6.

src/core.c

@@ -4735,7 +4735,7 @@ static void PollInputEvents(void)
             CORE.Input.Gamepad.currentState[i][GAMEPAD_BUTTON_LEFT_TRIGGER_2] = (char)(CORE.Input.Gamepad.axisState[i][GAMEPAD_AXIS_LEFT_TRIGGER] > 0.1);
             CORE.Input.Gamepad.currentState[i][GAMEPAD_BUTTON_RIGHT_TRIGGER_2] = (char)(CORE.Input.Gamepad.axisState[i][GAMEPAD_AXIS_RIGHT_TRIGGER] > 0.1);
 
-            CORE.Input.Gamepad.axisCount = GLFW_GAMEPAD_AXIS_LAST;
+            CORE.Input.Gamepad.axisCount = GLFW_GAMEPAD_AXIS_LAST + 1;
         }
     }