nios2: Add NEEK Temprei Devicetree

Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>
nios2: configs: Update neek_defconfig

This defconfig is just a workaround Buildroot's lack
of proper devicetree support.

Signed-off-by: Ezequiel Garcia <ezequiel@vanguardiasur.com.ar>