perf probe: Annotate variable initialization

Annotate away this false positive warning on older GCCs:

    cc1: warnings being treated as errors
    builtin-probe.c: In function ‘parse_probe_event’:
    builtin-probe.c:72: warning: ‘nc’ is used uninitialized in this function

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Masami Hiramatsu <mhiramat@redhat.com>
LKML-Reference: <1257254947-16789-1-git-send-email-acme@infradead.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

tools/perf/builtin-probe.c

@@ -69,7 +69,7 @@ static struct {
 static void parse_probe_point(char *arg, struct probe_point *pp)
 {
 	char *ptr, *tmp;
-	char c, nc;
+	char c, nc = 0;
 	/*
 	 * <Syntax>
 	 * perf probe SRC:LN