Allow MTD_NAND_GPMI_NAND to be built as module.
Signed-off-by: NFabio Estevam <fabio.estevam@freescale.com>
Signed-off-by: NArtem Bityutskiy <artem.bityutskiy@linux.intel.com>
Signed-off-by: NDavid Woodhouse <David.Woodhouse@intel.com>