perf hists: Allow for max_stack greater than PERF_MAX_STACK_DEPTH

Use the max_stack value instead of PERF_MAX_STACK_DEPTH so that
arbitrary-sized callchains can be supported.

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lkml.kernel.org/r/1443186956-18718-17-git-send-email-adrian.hunter@intel.com


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>