linux-wandboard

usb/xhci: update a comment regarding the BOS descriptor to reflect the code

The comment is a quote of Alan Stern and reflects the data structure
better than the the initial comment.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Sarah Sharp <sarah.a.sharp@linux.intel.com>