mtd: nand: pxa3xx: enable NAND controller if the SoC needs it

Based on Linux kernel commit fc256f5789cb ("mtd: nand: pxa3xx: enable
NAND controller if the SoC needs it"). This commit adds support for the
Armada 8040 nand controller.

The kernel commit says this:

    Marvell recent SoCs like A7k/A8k do not boot with NAND flash
    controller activated by default. Enabling the controller is a matter
    of writing in a system controller register that may also be used for
    other NAND related choices.

Reviewed-by: Stefan Roese <sr@denx.de>
Signed-off-by: Shmuel Hazan <shmuel.h@siklu.com>
Signed-off-by: Baruch Siach <baruch@tkos.co.il>