usb: store the new usb 3.1 SuperSpeedPlus device capability descriptor

If a device supports usb 3.1 SupeerSpeedPlus Gen2 speeds it povides
a SuperSpeedPlus device capability descriptor as a part of its
BOS descriptor. If we find one while parsing the BOS then save it
togeter with the other device capabilities found in the BOS

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