dt-bindings: mtd: sunxi: Add new compatible

The A23/A33 NAND controller is slightly different than the A10+ ones,
eg. DMA handling is a bit different and a few register offsets
changed.

Introduce a new compatible to represent this version of the IP.

Also append '-controller' to the new compatible (which is required for
new compatibles) as this is describing a NAND controller and not a
NAND chip.

Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>