common/config_defaults.h: make CONFIG_BOOTM_VXWORKS default configuration

Signed-off-by: Miao Yan <miao.yan@windriver.com>
diff --git a/include/config_defaults.h b/include/config_defaults.h
index 567b46c..ad08c1d 100644
--- a/include/config_defaults.h
+++ b/include/config_defaults.h
@@ -14,6 +14,7 @@
 #define CONFIG_BOOTM_NETBSD 1
 #define CONFIG_BOOTM_PLAN9 1
 #define CONFIG_BOOTM_RTEMS 1
+#define CONFIG_BOOTM_VXWORKS 1
 
 #define CONFIG_GZIP 1
 #define CONFIG_ZLIB 1