find a clock with a clock name

and add a 'find' ops.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
diff --git a/display.h b/display.h
index f9a762c..fe084cb 100644
--- a/display.h
+++ b/display.h
@@ -18,6 +18,7 @@
 struct display_ops {
 	int (*display)(void);
 	int (*select)(void);
+	int (*find)(const char *);
 };
 
 extern int display_print_line(int window, int line, char *str,