dt-bindings: mtd: nand-controller: Fix the reg property description

dt-bindings: mtd: nand-controller: Fix the reg property description

The reg property of a NAND device always references the chip-selects.
The ready/busy lines are described in the nand-rb property. I believe
this was a harmless copy/paste error during the conversion to yaml.

Fixes: 212e49693592 ("dt-bindings: mtd: Add YAML schemas for the generic NAND options")
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Acked-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/linux-mtd/20211216111654.238086-2-miquel.raynal@bootlin.com