perf annotate: Avoid TUI crash when navigating in the annotation of recursive functions

In 'perf report', entering a recursive function from inside of itself
(either directly of indirectly through some other function) results in
calling symbol__annotate2 multiple() times, and freeing the whole
disassembly when exiting from the innermost instance.

The first issue causes the function's disassembly to be duplicated, and
the latter a heap use-after-free (and crash) when trying to access the
disassembly again.

I reproduced the bug on perf 5.11.22 (Ubuntu 20.04.3 LTS) and 5.16.rc8
with the following testcase (compile with gcc recursive.c -o recursive).
To reproduce:

- perf record ./recursive
- perf report
- enter fibonacci and annotate it
- move the cursor on one of the "callq fibonacci" instructions and press enter
  - at this point there will be two copies of the function in the disassembly
- go back by pressing q, and perf will crash

  #include <stdio.h>

  int fibonacci(int n)
  {
      if(n <= 2) return 1;
      return fibonacci(n-1) + fibonacci(n-2);
  }

  int main()
  {
      printf("%d\n", fibonacci(40));
  }

This patch addresses the issue by annotating a function and freeing the
associated memory on exit only if no annotation is already present, so
that a recursive function is only annotated on entry.

Signed-off-by: Dario Petrillo <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexander Shishkin <[email protected]>
Cc: Jiri Olsa <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: Namhyung Kim <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: [email protected]
Link: http://lore.kernel.org/lkml/[email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

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