USB HID interface descriptor does not have an interface string

[adamgreig]

https://github.com/probe-rs/hs-probe-firmware/blob/master/firmware/src/usb/dap_v1.rs#L86

I don't fully understand why the interface() method here doesn't take a name, but the interface_alt() method we use on the v2 interface does; in any event CMSIS-DAP says we should have "CMSIS-DAP" in the interface string on composite devices, so we should probably add this somehow.