Fix USB port in input-usbmouse test

The default USB controller only has two ports.

tests/qemuxml2argvdata/qemuxml2argv-input-usbmouse-addr.args

@@ -20,5 +20,5 @@ QEMU_AUDIO_DRV=none \
 -usb \
 -drive file=/dev/HostVG/QEMUGuest1,format=raw,if=none,id=drive-ide0-0-0 \
 -device ide-drive,bus=ide.0,unit=0,drive=drive-ide0-0-0,id=ide0-0-0 \
--device usb-mouse,id=input0,bus=usb.0,port=4 \
+-device usb-mouse,id=input0,bus=usb.0,port=2 \
 -device virtio-balloon-pci,id=balloon0,bus=pci.0,addr=0x3

tests/qemuxml2argvdata/qemuxml2argv-input-usbmouse-addr.xml

@@ -22,7 +22,7 @@
     <controller type='usb' index='0'/>
     <controller type='ide' index='0'/>
     <input type='mouse' bus='usb'>
-      <address type='usb' bus='0' port='4'/>
+      <address type='usb' bus='0' port='2'/>
     </input>
   </devices>
 </domain>