arm64: dts: qcom: sm8250: Add sm8250 dts file

Add sm8250 devicetree file for SM8250 SoC and SM8250 MTP platform.
This file adds the basic nodes like cpu, psci and other required
configuration for booting up to the serial console.

Signed-off-by: Venkata Narendra Kumar Gutta <vnkgutta@codeaurora.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Link: https://lore.kernel.org/r/20200310050910.506854-1-vkoul@kernel.org
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>