virtio-devices: pci: skip activation of invalid queues

prepare_activator() called queue.is_valid() and only logged the failure,
then still pushed the queue to the activator. This would later panic.

Technically this is a fixup for:
a10508970 "virtio-devices: Support driver programming fewer queues"
But that's been in there since 2021. The intent was to allow a subset of
possible queues to be configured, but the invalid queues slipped through
too.

Signed-off-by: Dylan Reid <dgreid@fb.com>

virtio-devices/src/transport/pci_device.rs

@@ -807,7 +807,8 @@ impl VirtioPciDevice {
             }
 
             if !queue.is_valid(self.memory.memory().deref()) {
-                error!("Queue {queue_index} is not valid");
+                error!("Queue {queue_index} is not valid; skipping activation");
+                continue;
             }
 
             queues.push((