XHCI USB: disabled traces.
USB Stack: enable xHCI module lookup.

* also increase PhysicalMemoryAllocator max to 128KB instead of 16KB.
This translates in a 8MB-sized USB Stack Allocator area.
* tested OK on a Fresco Logic FL1009 USB 3.0 Host Controller but KO on a
Nec Corporation uPD720200 USB 3.0 Host Controller.
* tested a synched copy to a BFS partition on a Lacie USB3 disk takes about
8 seconds for 350MB versus 11 seconds on eHCI.