perf diff: Use perf_hpp__register_sort_field interface

Using perf_hpp__register_sort_field interface instead of directly adding
the entry.

Signed-off-by: Jiri Olsa <[email protected]>
Acked-by: Namhyung Kim <[email protected]>
Cc: Adrian Hunter <[email protected]>
Cc: David Ahern <[email protected]>
Cc: Noel Grandin <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

tools/perf/builtin-diff.c

@@ -1207,7 +1207,7 @@ static int ui_init(void)
 		BUG_ON(1);
 	}
 
-	list_add(&fmt->sort_list, &perf_hpp__sort_list);
+	perf_hpp__register_sort_field(fmt);
 	return 0;
 }