perf evlist: Amend mmap ref counting for the AUX area mmap

Reference counting of the mmap buffer does not work correctly when there
is an AUX area mmap also.

In snapshot mode it is not easy to know if the AUX area mmap buffer
contains usefull information. Equally the evlist does not know if the
recording is in sanpshot mode anyway.

Consequently, for now just assume the AUX area mmap always has data,
which will just cause the mmap buffer to remain mmapped for the duration
of the recording.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1429903807-20559-2-git-send-email-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>