perf hists: Consolidate __hists__add_*entry()

The __hists__add_{branch,mem}_entry() does almost the same thing that
__hists__add_entry() does.  Consolidate them into one.

Signed-off-by: Namhyung Kim <namhyung@kernel.org>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Rodrigo Campos <rodrigo@sdfg.com.ar>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/r/1383202576-28141-2-git-send-email-namhyung@kernel.org


[ Fixup clash with new COMM infrastructure ]
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>