arm64: dts: qcom: sm6125-sprout: correct ramoops pmsg-size

There is no 'msg-size' property in ramoops, so assume intention was for
'pmsg-size':

  sm6125-xiaomi-laurel-sprout.dtb: ramoops@ffc00000: Unevaluated properties are not allowed ('msg-size' was unexpected)

Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Link: https://lore.kernel.org/r/20230618114442.140185-4-krzysztof.kozlowski@linaro.org
Signed-off-by: Bjorn Andersson <andersson@kernel.org>