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/pcm052_defconfig b/configs/pcm052_defconfig
index c5c83e3..fdd8f38 100644
--- a/configs/pcm052_defconfig
+++ b/configs/pcm052_defconfig
@@ -29,6 +29,7 @@
 CONFIG_MTDPARTS_DEFAULT="mtdparts=NAND:640k(bootloader),128k(env1),128k(env2),128k(dtb),6144k(kernel),-(root)"
 CONFIG_CMD_UBI=y
 CONFIG_OF_CONTROL=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_NAND=y
 CONFIG_SYS_REDUNDAND_ENVIRONMENT=y
 CONFIG_SYS_RELOC_GD_ENV_ADDR=y