perf probe: Fix not to return non-matched file

Fix cu_find_realpath() not to return the last file path
if that is not matched to input pattern.

Signed-off-by: Masami Hiramatsu <mhiramat@redhat.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: systemtap <systemtap@sources.redhat.com>
Cc: DLE <dle-develop@lists.sourceforge.net>
LKML-Reference: <20100402165045.23551.47780.stgit@localhost6.localdomain6>
Signed-off-by: Ingo Molnar <mingo@elte.hu>