perf tools: Limit ordered events queue size

Add limit to the ordered events queue allocation. This way we will be
able to control the size of the queue buffers.

There's no limit at the moment (it's set to (u64) -1). The config code
will come in following patches.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Acked-by: David Ahern <dsahern@gmail.com>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jean Pihet <jean.pihet@linaro.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/n/tip-lw1ny3mk4ctb6su5ght5rsng@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>