[TIMOB-13614]iOS: Filter out iPad Splash Screens if the project is only for ipad

__TESTING INSTRUCTION__

* Create a sample project (You can use this [project]( https://dl.dropboxusercontent.com/u/43336767/splashtest.zip) has diff splash screens).
* build the app and bring it up in ipad sim. 
  ti build -p ios -Y ipad
* Make sure initial screen was iphone default/ iphone default@2x (retina sim)
* run the command again and verify the same again.
* Now build the app for device and install it in iPad. 
* Ensure the right splash screen.