arm64: dts: qcom: msm8996: Introduce IFC6640

Introduce a base dts for the Inforce 6640 Single Board Computer. This
initial commit boots to console on the uart and provides UFS and SD card
storage support.

Acked-by: Vinod Koul <vkoul@kernel.org>
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>