Spotlight not showing Bing results on iOS 8
There's only one location in Settings where I've seen reference to this. Try going to...

Settings &gt; General &gt; Spotlight Search


This is what I see when I go to those settings. You should be able to select the option there. If you don't see that option, you might try setting Bing as your default search engine for Safari. Let me know if that helps or what you find.

Hope that helps!