synphasor: General cleanup

synphasor: General cleanup

- col_...() shouldn't be under 'if (tree)';
- remove dead initializers;
- use proto_tree_add_subtree() in place of ..._add_text()/...add_subtree()
   in one more instance;
- tvb_length() --> tvb_reported_length();
- use 'proto tree *' variable instead of incorrect 'proto_item *' var in
   one instance;
- use SYNP_... for a few macro names to prevent any possible
   namespace collisions;
- fix some long-lines, indentation and whitespace.

Change-Id: I4e0a2e5d0b5e13b72a14ec6dd3779a7104534445
Reviewed-on: https://code.wireshark.org/review/6720
Reviewed-by: Bill Meier <wmeier@newsguy.com>