To disentangle util/sort.h a bit more.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-6kbf2cauas06rbqp15pyter5@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>