dt-bindings: memory: snps,dw-umctl2-ddrc: Replace opencoded numbers with macros

Xilinx ZynqMP DDRC-based example contains the opencoded numerical literals
in the IRQ lines definition. It doesn't seem justified since the
corresponding platform has well defined ARM GIC interface. Let's replace
the numbers with the corresponding macros then.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20220910195659.11843-2-Sergey.Semin@baikalelectronics.ru