[efi] Allow for non-PCI snpnet devices

We currently require information about the underlying PCI device to
populate the snpnet device's name and description.  If the underlying
device is not a PCI device, this will fail and prevent the device from
being registered.

Fix by falling back to populating the device description with
information based on the EFI handle, if no PCI device information is
available.

Signed-off-by: Michael Brown <mcb30@ipxe.org>

src/drivers/net/efi/snpnet.c

  *
  * @v efidev		EFI device
  * @v dev		Generic device to fill in
- * @ret rc		Return status code
  */
-static int snpnet_dev_info ( struct efi_device *efidev, struct device *dev ) {
+static void snpnet_dev_info ( struct efi_device *efidev, struct device *dev ) {
 	EFI_HANDLE device = efidev->device;
 	int rc;
 
 	/* Try getting underlying PCI device information */
 	if ( ( rc = snpnet_pci_info ( efidev, dev ) ) == 0 )
-		return 0;
+		return;
 
+	/* If we cannot get any underlying device information, fall
+	 * back to providing information about the EFI handle.
+	 */
 	DBGC ( device, "SNP %p %s could not get underlying device "
 	       "information\n", device, efi_handle_name ( device ) );
-	return -ENOTTY;
+	dev->desc.bus_type = BUS_TYPE_EFI;
+	snprintf ( dev->name, sizeof ( dev->name ), "SNP-%p", device );
 }
 
 /**
 	efidev_set_drvdata ( efidev, netdev );
 
 	/* Populate underlying device information */
-	if ( ( rc = snpnet_dev_info ( efidev, &snp->dev ) ) != 0 )
-		goto err_info;
+	snpnet_dev_info ( efidev, &snp->dev );
 	snp->dev.driver_name = "SNP";
 	snp->dev.parent = &efidev->dev;
 	list_add ( &snp->dev.siblings, &efidev->dev.children );
  err_shutdown:
  err_start:
 	list_del ( &snp->dev.siblings );
- err_info:
 	netdev_nullify ( netdev );
 	netdev_put ( netdev );
  err_alloc: