Add initial devicetree support for Hisilicon Hi3670 SoC which
is similar to Hi3660 SoC with NPU support.

This SoC has Octal core BigLittle CPUs in two clusters(4 * A53 & 4 * A73).

Only UART6 has been added for console support which is
pre configured by the bootloader. A fixed clock is sourcing
the UART6 which will get replaced by the clock driver when available.
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>