perf tests: Add pollfd growing test

perf tests: Add pollfd growing test

  [acme@ssdandy linux]$ perf test "Add fd"
  34: Add fd to pollfd array, making it autogrow             : Ok
  [acme@ssdandy linux]$ perf test -v "Add fd"
  34: Add fd to pollfd array, making it autogrow             :
  --- start ---
  test child forked, pid 19817

  before growing array:   2 [ 1, 2 ]
  after 3rd add_pollfd:   3 [ 1, 2, 35 ]
  after 4th add_pollfd:   4 [ 1, 2, 35, 88 ]
  test child finished with 0
  ---- end ----
  Add fd to pollfd array, making it autogrow: Ok
  [acme@ssdandy linux]$

Acked-by: Jiri Olsa <jolsa@kernel.org>
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-smflpyta146bzog7z0effjss@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>