UHCI isochronous support added

For those of you who are not following the haiku-commit mailing list, I’ve added the isochronous support to the UHCI driver. I’m working on a quickcam driver to test the code, but if someone of you out there, already have some very simply driver, that needs isochronous support, please contact me and help me with the testing.

The sooner I’m done with the testing, the sooner I’ll move on to the OHCI driver. ;-)