Commit d24d481b (usb-storage: Modify and export adjust_quirks so
that it can be used by uas) added the 'u' flag to the quirks module
parameter for usb-storage, but neglected to update the
documentation.  This patch adds the documentation.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Cc: stable <stable@vger.kernel.org>  # 3.15+
Signed-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>