perf ui gtk: Rename functions for consistency

We use double underscore characters to distinguish its subsystem and
actual function name.

Signed-off-by: Namhyung Kim <namhyung.kim@lge.com>
Acked-by: Pekka Enberg <penberg@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@gmail.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Pekka Enberg <penberg@kernel.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1335761711-31403-4-git-send-email-namhyung.kim@lge.com


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