qemu: add capabilities for virtio input devices
    
    Add capabilities for virtio-keyboard, virtio-mouse
    and virtio-tablet devices:
    
    name "virtio-keyboard-device", bus virtio-bus
    name "virtio-keyboard-pci", bus PCI
    name "virtio-mouse-device", bus virtio-bus
    name "virtio-mouse-pci", bus PCI
    name "virtio-tablet-device", bus virtio-bus
    name "virtio-tablet-pci", bus PCI
    
    Map both -device and -pci versions of the device to one capability.
    
    https://bugzilla.redhat.com/show_bug.cgi?id=1231114