Xone32c bNumConfigurations issue

[Tim Nugent]

Hi alsa-devel,

Having a few problems with the Xone32c though not sure if this is an ALSA
issue or general USB stack problem.

It's a USB soundcard that is supposed to have 4 inputs and 4 outputs. It
seems to have 2 USB configurations (bNumConfigurations : 0x2). When plugged
in, bConfigurationValue is 0x1 and only 2 inputs and 2 outputs show up.
Change this value to 0x2 and it shows up (as it should) as 4 inputs and 4
outputs. Here's the full USB description:

https://pastebin.com/DDPXv5c1

I can change the bConfigurationValue with this udev rule, or with a `echo 2
> /sys/bus/usb/devices/1-1.4/bConfigurationValue`:

https://gist.github.com/timnugent/ed65a79b2bd6c63788bfada3624756a4

This has all been working OK on Ubuntu 20.04 running kernel
5.4.0-33-generic. However, I just updated to 5.4.0-37-generic and now there
is only a single USB configuration (bNumConfigurations : 0x1) and
bConfigurationValue can't be changed to 0x2:

https://pastebin.com/th9VRH0q

echo 2 > /sys/bus/usb/devices/1-1.4/bConfigurationValue
bash: echo: write error: Invalid argument

So this could be a regression in snd_usb_audio, or maybe usbhid - which
`lsudb -t` says are the drivers. This behaviour (only 1 configuration) also
happens on a Raspberry Pi (Raspbian 4.19.66-v7+) - I haven't been able to
get it to work at all.

Thanks
Tim