vhost-iotlb: fix vhost_iotlb_del_range() documentation

Trivial change for the vhost_iotlb_del_range() documentation,
fixing the function name in the comment block.

Discovered with `make C=2 M=drivers/vhost`:
../drivers/vhost/iotlb.c:92: warning: expecting prototype for vring_iotlb_del_range(). Prototype was for vhost_iotlb_del_range() instead

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>
Link: https://lore.kernel.org/r/20210504135444.158716-1-sgarzare@redhat.com


Acked-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>