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>
int __attribute__((weak)) kvm_arch_set_irq_inatomic(
				struct kvm_kernel_irq_routing_entry *irq,
				struct kvm *kvm, int irq_source_id,
				int level,
				bool line_status)
{
	return -EWOULDBLOCK;
}

int __attribute__((weak)) kvm_arch_set_irq_inatomic(
				struct kvm_kernel_irq_routing_entry *irq,
				struct kvm *kvm, int irq_source_id,
				int level,
				bool line_status)
{
	return -EWOULDBLOCK;
}
