libperf: Adopt perf_mmap__read_init() from tools/perf

Move perf_mmap__read_init() from tools/perf to libperf and export it in
perf/mmap.h header.

And add pr_debug2()/pr_debug3() macros support, because the code is
using them.

Signed-off-by: Jiri 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/20191007125344.14268-11-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/util/python.c b/tools/perf/util/python.c
index 82a4fa6..64eec2a 100644
--- a/tools/perf/util/python.c
+++ b/tools/perf/util/python.c
@@ -1023,7 +1023,7 @@ static PyObject *pyrf_evlist__read_on_cpu(struct pyrf_evlist *pevlist,
 	if (!md)
 		return NULL;
 
-	if (perf_mmap__read_init(md) < 0)
+	if (perf_mmap__read_init(&md->core) < 0)
 		goto end;
 
 	event = perf_mmap__read_event(md);