[alsa-devel] ALSA: usb-audio: fix oops due to cleanup race when disconnecting

[pl bossart]

> Ah, I forgot to put my sign-off since I was waiting for any test
> result...  Has anyone tried it?
>

Tested-by: Pierre-Louis Bossart<pierre-louis.bossart at intel.com>

Discard my other messages, the patch seems to work fine when I don't
skip any steps...  I need more coffee and stop multitasking... I spent
15mn pluging and unpluging my headset without any issues.
Thanks Takashi and Clemens for the fix
-Pierre