armv8: ls2080a: Define CONFIG_ENV_OVERWRITE to overwrite serial and ethaddr

As the environment variables "serial#" and "ethaddr" need to be
overwriten by the users, CONFIG_ENV_OVERWRITE is defined to disable
the write protection. Anybody can change or delete these parameters.

Signed-off-by: Alison Wang <alison.wang@freescale.com>
Reviewed-by: York Sun <yorksun@freescale.com>

include/configs/ls2080a_common.h

@@ -253,6 +253,9 @@ unsigned long long get_qixis_addr(void);
 
 #define CONFIG_DISPLAY_CPUINFO
 
+/* Allow to overwrite serial and ethaddr */
+#define CONFIG_ENV_OVERWRITE
+
 /* Initial environment variables */
 #define CONFIG_EXTRA_ENV_SETTINGS		\
 	"hwconfig=fsl_ddr:bank_intlv=auto\0"	\