arm64: dts: qcom: sm8350: Drop standalone smem node

SM8350 is one of the last SoCs whose DTSI escaped the smem node
conversion. Use the newer memory-node binding instead of a memory *and*
smem node.

Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221219162618.873117-1-konrad.dybcio@linaro.org