fix forward declarations in opcua_serviceparser.h

The declarations from opcua_complextypeparser.h were used instead of the serviceparser ones, this is also fixed in our generator

Change-Id: I3d78d26a3b2b4995dfd4556720d29ecdd6960c4b
Reviewed-on: https://code.wireshark.org/review/4650
Petri-Dish: Alexis La Goutte <alexis.lagoutte@gmail.com>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Evan Huus <eapache@gmail.com>