vfio-mdev: remove some dead code

We set info.count to 1 in mtty_get_irq_info() so static checkers
complain that, "Why do we have impossible conditions?"  The answer is
that it seems to be left over dead code that can be safely removed.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Reviewed-by: Kirti Wankhede <kwankhede@nvidia.com>
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>