v4l2: fix and rationalize audio input selection
v4l2: fix and rationalize audio input selection

The audio capture capability flag is irrelevant. Instead the selected
video input specifies its allowed set of audio inputs.

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