sandbox: convert to common time functions

Convert sandbox to use common time functions.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>
diff --git a/include/configs/sandbox.h b/include/configs/sandbox.h
index bce4fcf..0884ad3 100644
--- a/include/configs/sandbox.h
+++ b/include/configs/sandbox.h
@@ -16,6 +16,8 @@
 
 #endif
 
+#define CONFIG_SYS_TIMER_RATE		1000000
+
 #define CONFIG_BOOTSTAGE
 #define CONFIG_BOOTSTAGE_REPORT