mtd: Add device-tree support to fsmc_nand

This patch adds support to configure the FSMC NAND driver (used amongst
others on SPEAr platforms) via device-tree instead of platform_data.

Signed-off-by: Stefan Roese <sr@denx.de>
Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>