perf tools: Use perf_mmap way to detect aux mmap

We will move this code to libperf shortly, so we need to free it of
'struct auxtrace_mmap' usage, because it won't be available in libperf
(for now).

The perf_event_mmap_page::aux_size is set when the aux mmap is mapped,
so the check is equivalent.
Signed-off-by: NJiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20191007125344.14268-9-jolsa@kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/mmap.c

@@ -107,7 +107,9 @@ union perf_event *perf_mmap__read_event(struct mmap *map)
 
 static bool perf_mmap__empty(struct mmap *map)
 {
-	return perf_mmap__read_head(map) == map->core.prev && !map->auxtrace_mmap.base;
+	struct perf_event_mmap_page *pc = map->core.base;
+
+	return perf_mmap__read_head(map) == map->core.prev && !pc->aux_size;
 }
 
 void perf_mmap__consume(struct mmap *map)