Eliminate proto_tree_add_text from packet-srvloc.c

Change-Id: I73a2270e259414f21a695d2b279df5b3cac27bb8
Reviewed-on: https://code.wireshark.org/review/6067
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>