Add the appropriate markup to get the kerneldoc comments out of
lib/debugobjects.c that have never seen the light of day until now.

A logical next step, left for the reader at the moment, is to move the
function descriptions *out* of debug-objects.rst and into the kerneldoc
comments themselves.

Signed-off-by: Jonathan Corbet <corbet@lwn.net>

A couple of the most minor heading tweaks, otherwise no changes to the text
itself beyond the mechanical conversion.

Note that the inclusion of the kerneldoc comments from the source has never
worked, since exported symbols were asked for and none of those functions
are exported to modules.  It doesn't work here either :)

Cc: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>