It only operates on the histograms, so no need for the encompassing
'struct annotation'.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: https://lkml.kernel.org/n/tip-2se2v7rrjil0kwqywks04ey2@git.kernel.orgSigned-off-by: NArnaldo Carvalho de Melo <acme@redhat.com>