usb-bus: remove "init" from USBDeviceClass struct

All usb-bus devices are realized by realize(),
remove init callback function from USBDeviceClass struct.
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NPaolo Bonzini <pbonzini@redhat.com>
Signed-off-by: NGerd Hoffmann <kraxel@redhat.com>

hw/usb/bus.c

@@ -113,8 +113,6 @@ static void usb_device_realize(USBDevice *dev, Error **errp)
 
     if (klass->realize) {
         klass->realize(dev, errp);
-    } else if (klass->init) {
-        klass->init(dev);
     }
 }
 

include/hw/usb.h

@@ -273,8 +273,6 @@ typedef void (*USBDeviceUnrealize)(USBDevice *dev, Error **errp);
 typedef struct USBDeviceClass {
     DeviceClass parent_class;
 
-    int (*init)(USBDevice *dev);
-
     USBDeviceRealize realize;
     USBDeviceUnrealize unrealize;