USB: unusual_devs entry for Nikon DSC D2Xs

This patch (as996) adds an unusual_devs entry for the Nikon DSC D2Xs
camera.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Cc: Phil Dibowitz <phil@ipom.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>