mtd: rawnand: denali: remove the old unified controller/chip DT support

Commit d8e8fd0e ("mtd: rawnand: denali: decouple controller and
NAND chips") supported the new binding for the separate controller/chip
representation, keeping the backward compatibility.

All the device trees in upstream migrated to the new binding.

Remove the support for the old binding.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>