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/k2hk_hs_evm_defconfig b/configs/k2hk_hs_evm_defconfig
index 55680e9..8fa2377 100644
--- a/configs/k2hk_hs_evm_defconfig
+++ b/configs/k2hk_hs_evm_defconfig
@@ -30,6 +30,7 @@
 CONFIG_MTDPARTS_DEFAULT="mtdparts=davinci_nand.0:1024k(bootloader)ro,512k(params)ro,-(ubifs)"
 CONFIG_CMD_UBI=y
 CONFIG_OF_CONTROL=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y
 CONFIG_NET_RANDOM_ETHADDR=y