Eliminate proto_tree_add_text from packet-lmp.c

Also "refactored" a few fields into proto_tree_add_bitmask calls.

Change-Id: I3a222b38e1992943d6ee4bd300026bc28c5bbb78
Reviewed-on: https://code.wireshark.org/review/4575
Petri-Dish: Michael Mann <mmann78@netscape.net>
Tested-by: Petri Dish Buildbot <buildbot-no-reply@wireshark.org>
Reviewed-by: Michael Mann <mmann78@netscape.net>