arm64: dts: Add dts files for Hisilicon Hi3660 SoC
Add initial dtsi file to support Hisilicon Hi3660 SoC with
support of Octal core CPUs in two clusters(4 * A53 & 4 * A73).
Also add dts file to support HiKey960 development board which
based on Hi3660 SoC.
The output console is earlycon "earlycon=pl011,0xfdf05000".
And the con_init uart5 with a fixed clock, which already
configured at bootloader.
When clock is available, the uart5 will be modified.