[smartplaylist] use values as passed by the user when filtering by video resolution

This fixes an issue where certain video items are not listed within smart playlists due to the fact we're calculating min and max values based on the actual value passed by the user.

Issue on the forum: http://forum.kodi.tv/showthread.php?tid=109809&pid=1866903#pid1866903

@Montellese for review please.