perf annotate: Move rb_node to struct annotation_line

Move rb_node to struct annotation_line to make struct annotation_line
the rb tree node for sorted lines used in both stdio and TUI code.

This way we can unite the sorted lines lines codes for both TUI and
stdio in the following patches.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: David Ahern <dsahern@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20171011150158.11895-14-jolsa@kernel.org


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>