cifs: convert send_nt_cancel into a version specific op

For SMB2, this should be a no-op. Obviously if we wanted to do something
for the SMB2 case, we could also define an operation here for it.

Signed-off-by: Jeff Layton <jlayton@redhat.com>
Signed-off-by: Pavel Shilovsky <piastry@etersoft.ru>
3 files changed