Removed unused usings. (#3593)

* Removed unused usings.

* Added back using, now that it's used.

* Removed extra whitespace.

Ryujinx.Audio.Backends.SDL2/SDL2HardwareDeviceDriver.cs

@@ -4,7 +4,6 @@ using Ryujinx.Memory;
 using Ryujinx.SDL2.Common;
 using System;
 using System.Collections.Concurrent;
-using System.Runtime.InteropServices;
 using System.Threading;
 
 using static Ryujinx.Audio.Integration.IHardwareDeviceDriver;