usb: device_next: cdc_acm: allow setting the interface description

Add a interface-name string for the CDC-ACM node, this allow setting a
string that is then set as iInterface, which can then be used downstream
in an udev rule such as:

SUBSYSTEM=="tty", ACTION=="add",
ATTRS{interface}=="my interface descriptor",
SYMLINK+="tty-my-device"

To create known aliases for these ports.

Signed-off-by: Fabio Baltieri <fabiobaltieri@google.com>