usb: xhci: remove xhci_debug_trb()

Every XHCI TRB has already been traced by the trb trace events.
It is unnecessary to put the same message in kernel log. This
patch removes xhci_debug_trb().

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Mathias Nyman <mathias.nyman@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>