mtd: nand: fix ONFI parameter page layout

src_ssync_features field is only 1 byte large, and the 4th reserved area
is actually 8 bytes large.

Fixes: d1e1f4e4

 ("mtd: nand: add support for reading ONFI parameters from NAND device")
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>
Signed-off-by: Brian Norris <computersforpeace@gmail.com>