dt-bindings: nand: meson: Fix 'nand-rb' property

Add description of 'nand-rb' property. Use "Fixes" because this property
must be supported since the beginning.

Fixes: fbc00b5e ("dt-bindings: nand: meson: convert txt to yaml")
Signed-off-by: Arseniy Krasnov <AVKrasnov@sberdevices.ru>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>
Link: https://lore.kernel.org/linux-mtd/20230608044728.1328506-2-AVKrasnov@sberdevices.ru