cosmetic: fix doxygen comment markers

There has obviously been a misunderstanding on how the doxygen comments work.
A comment marked '<' is for placing a comment *after* a member, to point back
to the item before it, typically

  enum foo {
  	thing, /*!< this is a thing */
	a_bobby,
  }

It does not make sense to place these above the item they are describing.

We actually don't use doxygen in the osmo-mgw build, but if we have doxygen
syntax, we might as well have the correct one.

Change-Id: I9e8ea0e3bd5ae5fcc0a6fae8e26e11baa8f35e27
4 files changed