arm64: dts: qcom: qdu1000: drop incorrect serial properties

The serial node does not use/allow address/size cells:

  qdu1000-idp.dtb: geniqup@9c0000: serial@99c000: Unevaluated properties are not allowed ('#address-cells', '#size-cells' were unexpected)

Fixes: 6bd20c54 ("arm64: dts: qcom: Add base QDU1000/QRU1000 DTSIs")
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20230308125906.236885-3-krzysztof.kozlowski@linaro.org