virtio: remove useless declaration of virtio_net_init()

commit 1773d9ee (virtio-net: cleanup: init and exit function)
removed the definition of virtio_net_init(), but didn't remove its
declaration in the header.  Clean that up.

Cc: Markus Armbruster <armbru@redhat.com>
Signed-off-by: NGonglei <arei.gonglei@huawei.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>

include/hw/virtio/virtio.h

@@ -230,9 +230,6 @@ int virtio_set_features(VirtIODevice *vdev, uint32_t val);
 /* Base devices.  */
 typedef struct VirtIOBlkConf VirtIOBlkConf;
 struct virtio_net_conf;
-VirtIODevice *virtio_net_init(DeviceState *dev, NICConf *conf,
-                              struct virtio_net_conf *net,
-                              uint32_t host_features);
 typedef struct virtio_serial_conf virtio_serial_conf;
 typedef struct VirtIOSCSIConf VirtIOSCSIConf;
 typedef struct VirtIORNGConf VirtIORNGConf;