[linux] Give tap devices a name and bus type

Give tap devices a meaningful name, and avoid segmentation faults when
attempting to retrieve ${net0/bustype} by assigning a new bus type for
tap devices.

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

src/drivers/linux/tap.c

@@ -216,6 +216,9 @@ static int tap_probe(struct linux_device *device, struct linux_device_request *r
 	}
 
 	nic->interface = if_setting->value;
+	snprintf ( device->dev.name, sizeof ( device->dev.name ), "%s",
+		   nic->interface );
+	device->dev.desc.bus_type = BUS_TYPE_TAP;
 	if_setting->applied = 1;
 
 	/* Apply rest of the settings */