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/aristainetos2c_defconfig b/configs/aristainetos2c_defconfig
index 4f6b9b9..9e1116b 100644
--- a/configs/aristainetos2c_defconfig
+++ b/configs/aristainetos2c_defconfig
@@ -55,6 +55,7 @@
 CONFIG_OF_LIST="imx6dl-aristainetos2c_4 imx6dl-aristainetos2c_7"
 CONFIG_DTB_RESELECT=y
 CONFIG_MULTI_DTB_FIT=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_SPI_FLASH=y
 CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y