conf: Rework virDomainDeviceDefParse
conf: Rework virDomainDeviceDefParse

When adding a new domain device, it is fairly easy to forget to add
corresponding piece into virDomainDeviceDefParse. However, if the
internal structure is changed to one bit switch() the compiler will warn
about not handled enum item.

datto/libvirt,VenkatDatta/libvirt,olafhering/libvirt,jfehlig/libvirt,crobinso/libvirt,shugaoye/libvirt,olafhering/libvirt,elmarco/libvirt,fabianfreyer/libvirt,jfehlig/libvirt,libvirt/libvirt,taget/libvirt,rlaager/libvirt,fabianfreyer/libvirt,taget/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,andreabolognani/libvirt,datto/libvirt,andreabolognani/libvirt,zippy2/libvirt,cbosdo/libvirt,shugaoye/libvirt,jfehlig/libvirt,fabianfreyer/libvirt,rlaager/libvirt,shugaoye/libvirt,shugaoye/libvirt,VenkatDatta/libvirt,fabianfreyer/libvirt,rlaager/libvirt,zhlcindy/libvirt-1.1.4-maintain,olafhering/libvirt,jardasgit/libvirt,zhlcindy/libvirt-1.1.4-maintain,agx/libvirt,agx/libvirt,VenkatDatta/libvirt,cbosdo/libvirt,libvirt/libvirt,agx/libvirt,crobinso/libvirt,VenkatDatta/libvirt,olafhering/libvirt,jardasgit/libvirt,jfehlig/libvirt,nertpinx/libvirt,crobinso/libvirt,zhlcindy/libvirt-1.1.4-maintain,libvirt/libvirt,agx/libvirt,eskultety/libvirt,nertpinx/libvirt,eskultety/libvirt,taget/libvirt,eskultety/libvirt,datto/libvirt,elmarco/libvirt,libvirt/libvirt,elmarco/libvirt,nertpinx/libvirt,zippy2/libvirt,nertpinx/libvirt,taget/libvirt,datto/libvirt,jardasgit/libvirt,zhlcindy/libvirt-1.1.4-maintain,shugaoye/libvirt,VenkatDatta/libvirt,eskultety/libvirt,elmarco/libvirt,rlaager/libvirt,elmarco/libvirt,eskultety/libvirt,zippy2/libvirt,cbosdo/libvirt,jardasgit/libvirt,rlaager/libvirt,agx/libvirt,andreabolognani/libvirt,taget/libvirt,fabianfreyer/libvirt,zhlcindy/libvirt-1.1.4-maintain,crobinso/libvirt,jardasgit/libvirt,cbosdo/libvirt,zippy2/libvirt,cbosdo/libvirt,nertpinx/libvirt,datto/libvirt