perf probe: Remove incorrect symbol check for --list

Remove unneeded symbol check for --list option.

This code actually checks whether the given symbol exists in the kernel.
But this is incorrect for online kernel/module and offline module too:

 - For online kernel/module, the kprobes itself already
  ensured the symbol exist in the kernel.
 - For offline module, this code can't access the offlined
  modules. Ignore it.
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: "David A. Long" <dave.long@linaro.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: yrl.pp-manager.tt@hitachi.com
Link: http://lkml.kernel.org/r/20140206053206.29635.7453.stgit@kbuild-fedora.yrl.intra.hitachi.co.jpSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/util/probe-event.c

@@ -739,14 +739,6 @@ int show_available_vars(struct perf_probe_event *pevs, int npevs,
 static int kprobe_convert_to_perf_probe(struct probe_trace_point *tp,
 					struct perf_probe_point *pp)
 {
-	struct symbol *sym;
-
-	sym = __find_kernel_function_by_name(tp->symbol, NULL);
-	if (!sym) {
-		pr_err("Failed to find symbol %s in kernel.\n", tp->symbol);
-		return -ENOENT;
-	}
-
 	return convert_to_perf_probe_point(tp, pp);
 }