ARM: Panda: Add flag to allow runtime enviroment varibale mods

Add the flag to allow runtime enviroment variable modifications.
This is being added so that the board-name can be modified at runtime
to indicate either a panda(4430) or a panda-es(4460)

Signed-off-by: Dan Murphy <dmurphy@ti.com>

include/configs/omap4_panda.h

@@ -66,4 +66,6 @@
 
 #define CONFIG_SYS_PROMPT		"Panda # "
 
+#define CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
+
 #endif /* __CONFIG_PANDA_H */