MFC r227342. Note that the original commit message, reproduced below, has

MFC r227342.  Note that the original commit message, reproduced below, has
error.  The final sentence should read "*without* CTF data".

 The in-kernel CTF parser caches the result of its first attempt to parse
 CTF data from a module.  On subsequent attempts to retrieve CTF data for
 a module, return an error if there no CTF data.

 This fixes a panic if you try to enable fbt probes on a module with CTF
 data twice.

Approved by:	re (kib)

git-svn-id: svn://svn.freebsd.org/base/releng/9.0@227969 ccf9f872-aa2e-dd11-9fc8-001c23d0bc1f