Clamp MediaPlayer volume to [0, 1] range

Fixes #2362

Verified XNA behaves the same way with:

```c#
var volBefore = MediaPlayer.Volume;
MediaPlayer.Volume = 2;
var volAfter = MediaPlayer.Volume;
MediaPlayer.Volume = float.NegativeInfinity;
var volAfter2 = MediaPlayer.Volume;
```

Without whitespace:
https://github.com/danzel/MonoGame/commit/edccac94988b64d3c12ec6409d925c8e31022541?w=1