highbank: enable keyed autoboot stop

Restrict autoboot interruption to "s" or "d" keys. This will prevent some
unwanted stopping and also allow disabling the reset on command timeout.

Signed-off-by: Rob Herring <rob.herring@calxeda.com>

include/configs/highbank.h

@@ -88,6 +88,8 @@
 #define CONFIG_BOOTDELAY		2
 #define CONFIG_BOOT_RETRY_TIME		-1
 #define CONFIG_RESET_TO_RETRY
+#define CONFIG_AUTOBOOT_KEYED
+#define CONFIG_AUTOBOOT_PROMPT "Autobooting in %d seconds...\nPress <s> to stop or <d> to delay\n", bootdelay
 
 /*
  * Miscellaneous configurable options