Convert CONFIG_ENV_OVERWRITE to Kconfig

This converts the following to Kconfig:
   CONFIG_ENV_OVERWRITE

Signed-off-by: Adam Ford <aford173@gmail.com>
[trini: Rerun migration, remove some comments]
Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/ls2088ardb_tfa_SECURE_BOOT_defconfig b/configs/ls2088ardb_tfa_SECURE_BOOT_defconfig
index d4abef1..15e1a17 100644
--- a/configs/ls2088ardb_tfa_SECURE_BOOT_defconfig
+++ b/configs/ls2088ardb_tfa_SECURE_BOOT_defconfig
@@ -34,6 +34,7 @@
 CONFIG_CMD_CACHE=y
 CONFIG_MP=y
 CONFIG_OF_CONTROL=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_NET_RANDOM_ETHADDR=y
 CONFIG_DM=y
 CONFIG_SATA_CEVA=y