mtd: rawnand: sunxi: add support for H6/H616 nand controller

mtd: rawnand: sunxi: add support for H6/H616 nand controller

Introduce H6/H616 NAND controller support for U-Boot

The H616 NAND controller has the same base as A10/A23, with some
differences:
- MDMA is based on chained buffers
- its ECC supports up to 80bit per 1024bytes
- some registers layouts are a bit different, mainly due do the stronger
  ECC.
- it uses USER_DATA_LEN registers along USER_DATA registers.
- it needs a specific clock for ECC and MBUS.

Introduce the basic support, with ECC and scrambling, but without
DMA/MDMA.

Tested on Whatsminer H616 board (with and without scrambling, ECC)

Signed-off-by: Richard Genoud <richard.genoud@bootlin.com>
Signed-off-by: Michael Trimarchi <michael@amarulasolutions.com>