perf tools: Put caller above callee in --children mode

The __hpp__sort_acc() sorts entries using callchain depth in order to
put callers above in children mode.  But it assumed the callchain order
was callee-first.  Now default (for children) is caller-first so the
order of entries is reverted.

For example, consider following case:

  $ perf report --no-children
  ..l
  # Overhead  Command  Shared Object        Symbol
  # ........  .......  ...................  ..........................
  #
      99.44%  a.out    a.out                [.] main
              |
              ---main
                 __libc_start_main
                 _start

Then children mode should show 'start' above '__libc_start_main' since
it's the caller (parent) of the __libc_start_main.  But it's reversed:

  # Children      Self  Command  Shared Object    Symbol
  # ........  ........  .......  ...............  .....................
  #
      99.61%     0.00%  a.out    libc-2.25.so     [.] __libc_start_main
      99.61%     0.00%  a.out    a.out            [.] _start
      99.54%    99.44%  a.out    a.out            [.] main

This patch fixes it.

  # Children      Self  Command  Shared Object    Symbol
  # ........  ........  .......  ...............  .....................
  #
      99.61%     0.00%  a.out    a.out            [.] _start
      99.61%     0.00%  a.out    libc-2.25.so     [.] __libc_start_main
      99.54%    99.44%  a.out    a.out            [.] main

Signed-off-by: Namhyung Kim <[email protected]>
Acked-by: Jiri Olsa <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Arnaldo Carvalho de Melo <[email protected]>
Cc: Frederic Weisbecker <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Milian Wolff <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Yao Jin <[email protected]>
Cc: [email protected]
Link: http://lkml.kernel.org/r/[email protected]
Signed-off-by: Ingo Molnar <[email protected]>

tools/perf/ui/hist.c

@@ -210,6 +210,8 @@ static int __hpp__sort_acc(struct hist_entry *a, struct hist_entry *b,
 			return 0;
 
 		ret = b->callchain->max_depth - a->callchain->max_depth;
+		if (callchain_param.order == ORDER_CALLER)
+			ret = -ret;
 	}
 	return ret;
 }