Document the legacy and the new bindings for Marvell NAND controller.
The pxa3xx_nand.c driver does only support legacy bindings, which are
incomplete and inaccurate. A rework of this controller (called
marvell_nand.c) does support both.
Signed-off-by: Miquel Raynal <miquel.raynal@free-electrons.com> Reviewed-by: Rob Herring <robh@kernel.org> Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>