perf annotate: Check availability of annotate when processing samples

The TUI of perf report and top support annotation, but stdio and GTK
don't.  So it should be checked before calling hist_entry__inc_addr_
samples() to avoid wasting resources that will never be used.

perf annotate need it regardless of UI and sort keys, so the check
of whether to allocate resources should be on the tools that have
annotate as an option in the TUI, 'report' and 'top', not on the
function called by all of them.

It caused perf annotate on ppc64 to produce zero output, since the
buckets were not being allocated.

Reported-by: Anton Blanchard <anton@samba.org>
Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Cc: Anton Blanchard <anton@samba.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung.kim@lge.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1392859976-32760-1-git-send-email-namhyung@kernel.org
[ Renamed (report,top)__needs_annotate() to ui__has_annotation() ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>