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/P2041RDB_SRIO_PCIE_BOOT_defconfig b/configs/P2041RDB_SRIO_PCIE_BOOT_defconfig
index 2832a86..822a91b 100644
--- a/configs/P2041RDB_SRIO_PCIE_BOOT_defconfig
+++ b/configs/P2041RDB_SRIO_PCIE_BOOT_defconfig
@@ -24,6 +24,7 @@
 CONFIG_MP=y
 CONFIG_CMD_EXT2=y
 CONFIG_CMD_FAT=y
+CONFIG_ENV_OVERWRITE=y
 CONFIG_ENV_IS_IN_REMOTE=y
 CONFIG_ENV_ADDR=0xFFE20000
 CONFIG_FSL_CAAM=y