mtd: rawnand: Clarify the NV-DDR entries in the ONFI structure

Both src_sync_timing_mode and src_ssync_features entries of the ONFI
parameter page have been updated and now are named nvddr_timing_modes,
nvddr2_timing_modes and nvddr_nvddr2_features, which is much more
understandable for someone which do not know the history of the ONFI
specification. Update the relevant structure with regard to these
changes.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210505213750.257417-8-miquel.raynal@bootlin.com