usb: Fix signature of stub usb_host_device_open

This was a breakage of 3741715cf2.

Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Blue Swirl <blauwirbel@gmail.com>
diff --git a/usb-stub.c b/usb-stub.c
index 9c3fcea..b4e10c1 100644
--- a/usb-stub.c
+++ b/usb-stub.c
@@ -41,7 +41,7 @@
 }
 
 /* XXX: modify configure to compile the right host driver */
-USBDevice *usb_host_device_open(const char *devname)
+USBDevice *usb_host_device_open(USBBus *bus, const char *devname)
 {
     return NULL;
 }