ARM: stm32: remove unused CONFIG_AUTOBOOT

At this point, this is not referenced from anywhere, so remove it
(but it will be re-added later for a different meaning).

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/include/configs/stm32f429-discovery.h b/include/configs/stm32f429-discovery.h
index 8bbe580..f05c1aa 100644
--- a/include/configs/stm32f429-discovery.h
+++ b/include/configs/stm32f429-discovery.h
@@ -82,8 +82,6 @@
 	"bootcmd_romfs=setenv bootargs ${bootargs} ${bootargs_romfs};" \
 	"bootm 0x08044000 - 0x08042000\0"
 
-#define CONFIG_AUTOBOOT
-
 /*
  * Command line configuration.
  */