usb: chipidea: debug: check before accessing ci_role

commit 0340ff83 upstream.

ci_role BUGs when the role is >= CI_ROLE_END.
Signed-off-by: Michael Thalmeier <michael.thalmeier@hale.at>
Signed-off-by: Peter Chen <peter.chen@nxp.com>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

drivers/usb/chipidea/debug.c

@@ -286,7 +286,8 @@ static int ci_role_show(struct seq_file *s, void *data)
 {
 	struct ci_hdrc *ci = s->private;
 
-	seq_printf(s, "%s\n", ci_role(ci)->name);
+	if (ci->role != CI_ROLE_END)
+		seq_printf(s, "%s\n", ci_role(ci)->name);
 
 	return 0;
 }