configs: ls1012a/ls1046a: Add CONFIG_ENV_OVERWRITE in defconfig

CONFIG_ENV_OVERWRITE disables write protection on various environment
variables like "ethaddr" and "serial".

Enable this config in LS1046A and LS1012A defconfigs. This resolves an
error while setting multiple values of "ethaddr" variable.

Before the change:
=> setenv ethaddr 00:E0:0C:00:06:0
=> setenv ethaddr 00:E0:0C:00:06:1
Error: Can't overwrite "ethaddr"
Error inserting "ethaddr" variable, errno=1

After the change:
=> setenv ethaddr 00:E0:0C:00:06:0
=> setenv ethaddr 00:E0:0C:00:06:1

Signed-off-by: Kuldeep Singh <kuldeep.singh@nxp.com>
Reviewed-by: Priyanka Jain <priyanka.jain@nxp.com>
diff --git a/configs/ls1012ardb_qspi_defconfig b/configs/ls1012ardb_qspi_defconfig
index 439bd93..f500479 100644
--- a/configs/ls1012ardb_qspi_defconfig
+++ b/configs/ls1012ardb_qspi_defconfig
@@ -35,6 +35,7 @@
 # CONFIG_CMD_SETEXPR is not set
 CONFIG_CMD_CACHE=y
 CONFIG_OF_CONTROL=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_SPI_FLASH=y
 CONFIG_ENV_ADDR=0x40300000
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y