board/BuR/tseries: reactivate NAND-board

The NAND-version has been become a bit orphan.
Now we need to reactivate it, so bring necessary things:

- loading devicetree
- switch control signal to correct pins
- setup pinmux
- default-environment

up to date.

Signed-off-by: Hannes Petermaier <oe5hpm@oevsv.at>