enable usb_audio in nightly builds

[tidux]

I have successfully built, booted, and run a @nightly-anyboot gcc2h target with the USB Audio driver enabled. It works with a C-Media Electronics, Inc. Audio Adapter (USB ID 0d8c:000c), and produces sound (although not the right sounds) with a Turtle Beach Amigo II (USB UD: 10f5:0211). Other than hotplug and compatibility fixes for specific models like the Amigo II, the driver is ready to use, and the remaining bugs will be found much more easily with a wider user base to test them. On a more personal note, the USB audio devices are much simpler to use than the nightmarish complexities of getting my Conexant HDA chipset into working with Haiku.

Attached is a patch to enable USB Audio.

[siarzhuk]

Thanks for feedback. You just lucky owner of the OHCI USB controller. Haiku has correct implementation of isochronous transfers for it. UHCI, EHCI and XHCI need to be refactored as described in #1045. Using usb_audio with such controller types crashes the system. That's why it is not in the image yet.

[pulkomandy]

Marked patch as obsolete, so it does not show in the "pending review" list. We will remember to do this when isochronous transfers are implemented well enough to not crash the system too much.