KVM: Don't accept obviously wrong gsi values via KVM_IRQFD

We cannot add routes for gsi values >= KVM_MAX_IRQ_ROUTES -- see
kvm_set_irq_routing(). Hence, there is no sense in accepting them
via KVM_IRQFD. Prevent them from entering the system in the first
place.

Signed-off-by: Jan H. Schönherr <jschoenh@amazon.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
to_ioeventfd(struct kvm_io_device *dev)
{
	return container_of(dev, struct _ioeventfd, dev);
}

to_ioeventfd(struct kvm_io_device *dev)
{
	return container_of(dev, struct _ioeventfd, dev);
}
