arm: socfpga: Add support for Denali NAND controller

Add common configuration bits for the Denali NAND controller and also
support for using it as a boot device in SPL.

Signed-off-by: Marek Vasut <marex@denx.de>
Cc: Dinh Nguyen <dinguyen@opensource.altera.com>
Cc: Chin Liang See <clsee@altera.com>