virtio: Add virtio::probe() helper

Add a new virtio::probe() helper function to simplify virtio driver
probing.

Signed-off-by: Pekka Enberg <penberg@cloudius-systems.com>

drivers/virtio.hh

@@ -176,6 +176,17 @@ protected:
     bool _cap_event_idx = false;
 };
 
+template <typename T, u16 ID>
+hw_driver* probe(hw_device* dev)
+{
+    if (auto pci_dev = dynamic_cast<pci::device*>(dev)) {
+        if (pci_dev->get_id() == hw_device_id(VIRTIO_VENDOR_ID, ID)) {
+            return new T(*pci_dev);
+        }
+    }
+    return nullptr;
+}
+
 }
 
 #endif