snow: Define CONFIG_AUTOBOOT_MENUKEY

This option is not used by any boards. To avoid needing to remove it as
dead code, add it to 'snow'.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/configs/snow_defconfig b/configs/snow_defconfig
index f474409..e5c7bdd 100644
--- a/configs/snow_defconfig
+++ b/configs/snow_defconfig
@@ -18,6 +18,8 @@
 # CONFIG_SPL_FRAMEWORK is not set
 CONFIG_SPL_TEXT_BASE=0x02023400
 CONFIG_SYS_PROMPT="snow # "
+CONFIG_USE_AUTOBOOT_MENUKEY=y
+CONFIG_AUTOBOOT_MENUKEY=33
 CONFIG_CMD_GPIO=y
 CONFIG_CMD_I2C=y
 CONFIG_CMD_MMC=y