arm: socfpga: Unreset NAND in U-Boot

Make sure the NAND reset is not asserted in full U-Boot.

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