dt-bindings: memory-controllers: ingenic,nemc: reference peripheral properties

Ingenic NAND / External Memory Controller has children with peripheral
properties, so it should reference the Memory Controller bus
Peripheral-specific schema.

Acked-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20230713152848.82752-2-krzysztof.kozlowski@linaro.org


Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>