Remove the use of pinfo->private_data from dissectors that just save it to restore it.

Change-Id: I13197cc48068bb35ee12a7023cfe5f76bbc4e264
Reviewed-on: https://code.wireshark.org/review/5486
Petri-Dish: Michael Mann <mmann78@netscape.net>
Reviewed-by: Michael Mann <mmann78@netscape.net>