dt-bindings: intel: add binding for Intel n6000

commit d84d4368c18cd7632460e037ee4f72303c59ec8b from
https://github.com/altera-opensource/linux-socfpga.git



[upstream commit af657d7f]

Add the binding string for the Agilex based Intel n6000 board.

Signed-off-by: Matthew Gerlach <matthew.gerlach@linux.intel.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Dinh Nguyen <dinguyen@kernel.org>
Signed-off-by: Wenlin Kang <wenlin.kang@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>