fhci-hub: no need to overwrite byte 3 of the Hub Descriptor

The code handling Get Hub Descriptor request copies data from root_hub_des[],
then overwrites byte 3 with real 'wHubCharacteristics' value. There's no need
to overwrite, we can substitute the real value right into root_hub_des[3].

Signed-off-by: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>