mtd: rawnand: onfi: Fix endianness when reading NV-DDR values

Without the use of le16_to_cpu(), these accesses would have been wrong
on a big-endian machine.

Reported-by: kernel test robot <lkp@intel.com>
Fixes: 45606518 ("mtd: rawnand: Add onfi_fill_nvddr_interface_config() helper")
Fixes: 9310668f ("mtd: rawnand: Retrieve NV-DDR timing modes from the ONFI parameter page")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210527084913.208635-1-miquel.raynal@bootlin.com