arm64: dts: qcom: msm8996: don't use empty memory node

We expect bootloader to full memory details but passing empty values
can give warning, so add a default value

Signed-off-by: Vinod Koul <vkoul@kernel.org>
Tested-by: Konrad Dybcio <konrad.dybcio@somainline.org>
Link: https://lore.kernel.org/r/20210308060826.3074234-13-vkoul@kernel.org


Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>