[Feature] Turn on CONFIG_DYNAMIC_DEBUG

In the 3.12 kernel, the xHCI driver will switch away from using CONFIG_USB_XHCI_HCD_DEBUGGING and switch to using dynamic
debugging. If distros have CONFIG_USB_DEBUG on and CONFIG_DYNAMIC_DEBUG off, the xHCI driver will spew tons and tons of debugging output to dmesg. This will effect performance of the system, as some debugging is printed in interrupt context. Distros should turn on CONFIG_DYNAMIC_DEBUG. This will cause the xHCI debugging to be off by default. Users can re-enable xHCI
debugging via a sysfs interface. This has the advantage that users won't need to recompile their kernel with CONFIG_USB_XHCI_HCD_DEBUGGING in order to get xHCI debugging out, which should help with distro and upstream triage.

External links: http://marc.info/?l=linux-usb&m=137277669328750&w=2

Schedule: kernel 3.12