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/ls2088aqds_tfa_defconfig b/configs/ls2088aqds_tfa_defconfig
index 85ec8ae..5db2e77 100644
--- a/configs/ls2088aqds_tfa_defconfig
+++ b/configs/ls2088aqds_tfa_defconfig
@@ -37,6 +37,7 @@
 CONFIG_OF_CONTROL=y
 CONFIG_OF_LIST="fsl-ls2080a-qds-42-x"
 CONFIG_MULTI_DTB_FIT=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_FLASH=y
 CONFIG_ENV_IS_IN_MMC=y
 CONFIG_ENV_IS_IN_SPI_FLASH=y