[d16-2] [GameController] GCGamepad is deprecated in the headers, so mark it as such. Fixes xamarin/maccore#1742. (#6428)

* [GameController] GCGamepad is deprecated in the headers, so mark it as such. Fixes xamarin/maccore#1742.

Fixes https://github.com/xamarin/maccore/issues/1742.

* Add attribute for tvOS too.

src/gamecontroller.cs

@@ -121,6 +121,9 @@ namespace GameController {
 
 	[iOS (7,0)]
 	[Mac (10,9, onlyOn64: true)]
+	[Deprecated (PlatformName.MacOSX, 10, 12)]
+	[Deprecated (PlatformName.iOS, 10, 0)]
+	[Deprecated (PlatformName.TvOS, 10, 0)]
 	[BaseType (typeof (NSObject))]
 	[DisableDefaultCtor] // return nil handle -> only exposed as getter
 	partial interface GCGamepad {