Actually, there is a way. You just need to copy DeviceSupport folder for iOS 7.1 from Older Xcode to the new one. It's located in:
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/7.1
If you don't have the 7.1 files anymore, you can download a previous version of XCode on https://developer.apple.com/download/more/, extract it, and then copy these files to following path
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/DeviceSupport/