virtio: fix map ops comment

@free will free the map handle not sync it. Fix the doc to match.

Fixes: bee8c7c ("virtio: introduce map ops in virtio core")
Message-Id: <f6ff1c7aff8401900bf362007d7fb52dfdb6a15b.1763026134.git.mst@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>

Author: mstsirkin

include/linux/virtio_config.h

@@ -177,7 +177,7 @@ struct virtio_config_ops {
  *      map: metadata for performing mapping
  *      size: the size of the buffer
  *      vaddr: virtual address of the buffer
- *      map_handle: the mapping address to sync
+ *      map_handle: the mapping address that needs to be freed
  *      attrs: unmapping attributes
  * @need_sync: if the buffer needs synchronization
  *      map: metadata for performing mapping