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/theadorable-x86-conga-qa3-e3845-pcie-x4_defconfig b/configs/theadorable-x86-conga-qa3-e3845-pcie-x4_defconfig
index 7cfe956..08cb9f1 100644
--- a/configs/theadorable-x86-conga-qa3-e3845-pcie-x4_defconfig
+++ b/configs/theadorable-x86-conga-qa3-e3845-pcie-x4_defconfig
@@ -49,6 +49,7 @@
 CONFIG_ISO_PARTITION=y
 CONFIG_AMIGA_PARTITION=y
 CONFIG_EFI_PARTITION=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_REGMAP=y