Fix pour Asus Xonar U5 card SPIF in USB-Audio.conf

[GitHub issues - edited <github@xxxxxxxxxxxxxxxx>]

alsa-project/alsa-lib issue #48 was edited from burningd0g:

It would be greatly apreciated to add the iec958 correct device in the default USB-Audio.conf for the Xonar USB sound card :

USB-Audio.pcm.iec958_device {
        ...
        "ASUS XONAR U5" 1
        "XONAR U5" 1
       ...
}

It would prevent me (and maybe some other people) to freak out on why it doesn't work out of the box! :)
I know the issue is also present on the U7 but i don't have all the possible device name for it.

Thanks!

Issue URL     : https://github.com/alsa-project/alsa-lib/issues/48
Repository URL: https://github.com/alsa-project/alsa-lib