rearranged control URB request conditionals

Rearranged conditionals for control URB request to limit variable scope.
Now there are 2 major branches based on weather the URB has setup data.

Change-Id: I67172c4e949bbda363ccf939d404957258b73840
Reviewed-on: https://code.wireshark.org/review/3847
Reviewed-by: Michael Mann <mmann78@netscape.net>
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Anders Broman <a.broman58@gmail.com>