MLK-22279-1 env: Add env_get_offset to override static env offset

MLK-22279-1 env: Add env_get_offset to override static env offset

Add env_get_offset interface to override static CONFIG_ENV_OFFSET,
and update env location driver to use env_get_offset. So for different
storage medium, we are able to store the env at different offset.

We don't support this feature when CONFIG_ENV_IS_EMBEDDED is set.

Signed-off-by: Ye Li <ye.li@nxp.com>
(cherry picked from commit 5b12d7cabb14bab9a95af7460b36c6c85db1b328)