perf, probe-finder: Build fix on Debian

Building chokes with:

 In file included from /usr/include/gelf.h:53,
                 from /usr/include/elfutils/libdw.h:53,
                 from util/probe-finder.h:61,
                 from util/probe-finder.c:39:
 /usr/include/libelf.h:98: error: expected specifier-qualifier-list before 'off64_t'
 [...]

Signed-off-by: Borislav Petkov <borislav.petkov@amd.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
LKML-Reference: <20100329164755.GA16034@aftab>
Signed-off-by: Ingo Molnar <mingo@elte.hu>