mtd: ndfc: fix typo in structure dereference

In commit 9d7948c5 (mtd: ndfc: use
ofpart through generic parsing) we dereference a non pointer type
causing the following compiler error:
drivers/mtd/nand/ndfc.c: In function 'ndfc_chip_init':
drivers/mtd/nand/ndfc.c:191: error: invalid type argument of '->' (have 'struct mtd_part_parser_data')

Fix that.

Signed-off-by: Tony Breeds <tony@bakeyournoodle.com>
Acked-by: Dmitry Eremin-Solenikov <dbaryshkov@gmail.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>