i2c: cp2615: fix serial string NULL-deref at probe

In the Linux kernel, the following vulnerability has been resolved: i2c: cp2615: fix serial string NULL-deref at probe The cp2615 driver uses the USB device serial string as the i2c adapter name but does not make sure that the string exists. Verify that the device has a serial number before accessing it to avoid triggering a NULL-pointer dereference (e.g. with malicious devices).