smegw01: Remove misuse of CONFIG_ENV_IS_NOWHERE

When using a list of writeable variables, the initial values come
from the built-in default environment since commit 5ab81058 ("env:
Complete generic support for writable list").

Remove unnecessary misuse of CONFIG_ENV_IS_NOWHERE as default environment.

Based on the fix done by commit b16fd7f7 ("imx6q: acc: Remove misuse
of env is nowhere driver").

Signed-off-by: Eduard Strehlau <eduard@lionizers.com>
Signed-off-by: Fabio Estevam <festevam@denx.de>