We were checking just if it was still on some rb tree, but that is not
the only way that this map can still have references, map->refcnt is
there exactly for this, use it.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-hany65tbeavsax7n3xvwl9pc@git.kernel.orgSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>