virtio-devices: Add set_notifier() method to VirtioInterrupt

It is currently left as unimplemented!().

No functional change intended as there are no callers.

Signed-off-by: Demi Marie Obenour <demiobenour@gmail.com>

fuzz/fuzz_targets/console.rs

@@ -148,6 +148,15 @@ impl VirtioInterrupt for NoopVirtioInterrupt {
     fn trigger(&self, _int_type: VirtioInterruptType) -> std::result::Result<(), std::io::Error> {
         Ok(())
     }
+
+    fn set_notifier(
+        &self,
+        _interrupt: u32,
+        _eventfd: Option<EventFd>,
+        _vm: &dyn hypervisor::Vm,
+    ) -> std::io::Result<()> {
+        unimplemented!()
+    }
 }
 
 fn setup_virt_queues(bytes: &[&[u8; QUEUE_DATA_SIZE]], base_addr: u64) -> Vec<Queue> {