vhost-backend: do not depend on CONFIG_VHOST_VSOCK

The vsock callbacks .vhost_vsock_set_guest_cid and
.vhost_vsock_set_running are the only ones to be conditional
on #ifdef CONFIG_VHOST_VSOCK.  This is different from any other
device-dependent callbacks like .vhost_scsi_set_endpoint, and it
also broke when CONFIG_VHOST_VSOCK was changed to a per-target
symbol.

It would be possible to also use the CONFIG_DEVICES include, but
really there is no reason for most virtio files to be per-target
so just remove the #ifdef to fix the issue.

Reported-by: Dov Murik <dovmurik@linux.ibm.com>
Fixes: 9972ae314f ("build: move vhost-vsock configuration to Kconfig")
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

hw/virtio/vhost-backend.c

@@ -203,7 +203,6 @@ static int vhost_kernel_get_vq_index(struct vhost_dev *dev, int idx)
     return idx - dev->vq_index;
 }
 
-#ifdef CONFIG_VHOST_VSOCK
 static int vhost_kernel_vsock_set_guest_cid(struct vhost_dev *dev,
                                             uint64_t guest_cid)
 {
@@ -214,7 +213,6 @@ static int vhost_kernel_vsock_set_running(struct vhost_dev *dev, int start)
 {
     return vhost_kernel_call(dev, VHOST_VSOCK_SET_RUNNING, &start);
 }
-#endif /* CONFIG_VHOST_VSOCK */
 
 static void vhost_kernel_iotlb_read(void *opaque)
 {
@@ -319,10 +317,8 @@ const VhostOps kernel_ops = {
         .vhost_set_owner = vhost_kernel_set_owner,
         .vhost_reset_device = vhost_kernel_reset_device,
         .vhost_get_vq_index = vhost_kernel_get_vq_index,
-#ifdef CONFIG_VHOST_VSOCK
         .vhost_vsock_set_guest_cid = vhost_kernel_vsock_set_guest_cid,
         .vhost_vsock_set_running = vhost_kernel_vsock_set_running,
-#endif /* CONFIG_VHOST_VSOCK */
         .vhost_set_iotlb_callback = vhost_kernel_set_iotlb_callback,
         .vhost_send_device_iotlb_msg = vhost_kernel_send_device_iotlb_msg,
 };