mtd: rawnand: renesas: Add new NAND controller driver

Introduce Renesas NAND controller driver which currently supports the
following features on R-Car Gen3 and RZ/N1 SoCs:
- All ONFI timing modes
- Different configurations of its internal ECC controller
- On-die (not tested) and software ECC support
- Several chips (not tested)
- Subpage accesses
- DMA and PIO

This controller was originally provided by Evatronix before being bought
by Cadence.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Tested-by: Ralph Siemsen <ralph.siemsen@linaro.org>
Acked-by: Wolfram Sang <wsa+renesas@sang-engineering.com>
Link: https://lore.kernel.org/linux-mtd/20211217142033.353599-3-miquel.raynal@bootlin.com