perf: Fix hist_entry__tui_annotate() build failure

When compiling perf on latest tip/master I see the following
error:

  cc1: warnings being treated as errors
  util/newt.c: In function 'hist_entry__tui_annotate':
  util/newt.c:764: warning: 'ret' is used uninitialized in
  this function make: *** [util/newt.o] Error 1

I think the problem was introduced by commit
13f499f0

Below is a patch that fixes the problem.

Signed-off-by: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
LKML-Reference: <20100629173226.GC23231@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>