Remove some unused fields from struct linker_file. They were added in

r172862 for use by the DTrace SDT framework but don't seem to have ever
been used.

MFC after:	2 weeks

sys/kern/kern_linker.c

@@ -583,8 +583,6 @@ linker_make_file(const char *pathname, linker_class_t lc)
 	lf->ndeps = 0;
 	lf->deps = NULL;
 	lf->loadcnt = ++loadcnt;
-	lf->sdt_probes = NULL;
-	lf->sdt_nprobes = 0;
 	STAILQ_INIT(&lf->common);
 	TAILQ_INIT(&lf->modules);
 	TAILQ_INSERT_TAIL(&linker_files, lf, link);

sys/sys/linker.h

@@ -92,10 +92,6 @@ struct linker_file {
      */
     int			nenabled;	/* number of enabled probes. */
     int			fbt_nentries;	/* number of fbt entries created. */
-    void		*sdt_probes;
-    int			sdt_nentries;
-    size_t		sdt_nprobes;
-    size_t		sdt_size;
 };
 
 /*