SX1: add CONFIG_STDOUT_USBTTY to enable preboot stdout redirect to usbtty

Signed-off-by: Jean-Christophe PLAGNIOL-VILLARD <plagnioj@jcrosoft.com>
diff --git a/include/configs/SX1.h b/include/configs/SX1.h
index fd1a3bd..34a5999 100644
--- a/include/configs/SX1.h
+++ b/include/configs/SX1.h
@@ -116,7 +116,9 @@
 #include <configs/omap1510.h>
 
 #define CONFIG_BOOTARGS		"mem=16M console=ttyS0,115200n8 root=/dev/mtdblock3 rw"
+#ifdef CONFIG_STDOUT_USBTTY
 #define CONFIG_PREBOOT		"setenv stdout usbtty;setenv stdin usbtty"
+#endif
 
 /*
  * Miscellaneous configurable options