Allows sounds to be cached for ios too

Playing ogg sounds on ios freezes the game for a moment before playing the sound. This simple fix allows sounds to be cached on ios with FlxG.sounds.add(), which solves the lag problem.
Merge pull request #963 from Vascofr/patch-2

Thanks, no reason I know of for android only here, maybe a future alternative is to use if #mobile, need to test more platforms.