mtd: rawnand: Add onfi_fill_nvddr_interface_config() helper

Same logic as for the SDR path, let's create a
onfi_fill_nvddr_interface_config() helper to fill an interface
configuration structure with NV-DDR timings, given a specific ONFI mode.

There is one additional thing to do compared to SDR mode: tCAD timing
can be fast or slow and this depends on an ONFI parameter page bit. By
default the slow value is declared in the timings structure definition,
but this helper can shrink it down if necessary.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20210505213750.257417-12-miquel.raynal@bootlin.com