ALSA: use IEC958 device when applicable (and small simplification)
ALSA: use IEC958 device when applicable (and small simplification)

Probable regression from 95a18cc9e66e7f06276052ae6411d494c6e8b6aa
(9 months old, I guess no developers use S/PDIF)

jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,krichter722/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,jomanmuk/vlc-2.1,xkfz007/vlc,shyamalschandra/vlc,krichter722/vlc,krichter722/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc,krichter722/vlc,vlc-mirror/vlc-2.1,xkfz007/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,xkfz007/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,krichter722/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,vlc-mirror/vlc-2.1,krichter722/vlc,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.1,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.2,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,vlc-mirror/vlc,shyamalschandra/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,shyamalschandra/vlc,vlc-mirror/vlc