env: Rename OVERWRITE_ETHADDR_ONCE to ENV_OVERWRITE_ETHADDR_ONCE

Rename the variable and add ENV_ prefix, so that all configuration
options which are related to environment would have an CONFIG_ENV_
prefix. No functional change.

Reviewed-by: Quentin Schulz <quentin.schulz@cherry.de>
Reviewed-by: Tom Rini <trini@konsulko.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
6 files changed