perf buildid-cache: Remove extra debugdir variables

perf buildid-cache: Remove extra debugdir variables

There's no need to copy over the buildid_dir into separate variable with
no change.

This is leftover from commit:
  45de34bbe3e1 perf buildid: add perfconfig option to specify buildid cache dir

that added global buildid_dir variable that holds cache directory, but
did not cleanup the debugdir copies.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Stephane Eranian <eranian@google.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Link: http://lkml.kernel.org/r/1417460789-13874-3-git-send-email-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>