vfio/spapr: Remove stale ioctl() call

This ioctl() call to VFIO_IOMMU_SPAPR_TCE_REMOVE was left over from an
earlier version of the code and has since been folded into
vfio_spapr_remove_window().

It wasn't caught because although the argument structure has been removed,
the libc function remove() means this didn't trigger a compile failure.
The ioctl() was also almost certain to fail silently and harmlessly with
the bogus argument, so this wasn't caught in testing.

Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
Reviewed-by: Alexey Kardashevskiy <aik@ozlabs.ru>