virDomainAudioCommonParse: Use virXMLProp*
virDomainAudioCommonParse: Use virXMLProp*

This strictens the parser to disallow negative values (interpreted as
`UINT_MAX + value + 1`) for attributes `voices` (typically 1),
`bufferLength` (measured in milliseconds), `frequency` (in Hz, typically
44100), and `channels` (typically 2 for stereo).

None of these properties benefit from or have a sensible use-case for
wrap-around behavior.

Signed-off-by: Tim Wiederhake <da93ee425e056cfcf1ddac9fc87851b25464abf4@redhat.com>
Reviewed-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>
Signed-off-by: Ján Tomko <4cab11cfb98d3c937327354a78eb07dbb6ee2bc6@redhat.com>

crobinso/libvirt,zippy2/libvirt,jfehlig/libvirt,olafhering/libvirt,jfehlig/libvirt,libvirt/libvirt,nertpinx/libvirt,olafhering/libvirt,libvirt/libvirt,nertpinx/libvirt,jfehlig/libvirt,crobinso/libvirt,crobinso/libvirt,nertpinx/libvirt,jfehlig/libvirt,nertpinx/libvirt,libvirt/libvirt,olafhering/libvirt,zippy2/libvirt,olafhering/libvirt,zippy2/libvirt,zippy2/libvirt,crobinso/libvirt,nertpinx/libvirt,libvirt/libvirt