perf tools: Set the maximum allowed stack from /proc/sys/kernel/perf_event_max_stack

There is an upper limit to what tooling considers a valid callchain,
and it was tied to the hardcoded value in the kernel,
PERF_MAX_STACK_DEPTH (127), now that this can be tuned via a sysctl,
make it read it and use that as the upper limit, falling back to
PERF_MAX_STACK_DEPTH for kernels where this sysctl isn't present.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Brendan Gregg <brendan.d.gregg@gmail.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Milian Wolff <milian.wolff@kdab.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-yjqsd30nnkogvj5oyx9ghir9@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/util.h

@@ -267,6 +267,7 @@ void sighandler_dump_stack(int sig);
 
 extern unsigned int page_size;
 extern int cacheline_size;
+extern unsigned int sysctl_perf_event_max_stack;
 
 struct parse_tag {
 	char tag;