arm64: dts: hisi: add pinctrl dtsi file for HiKey960 development board

Add pinctrl dtsi file for HiKey960 development board, enable
5 pinmux devices and 1 pinconf device, also include some nodes
of configurations for pins.

Signed-off-by: Wang Xiaoyin <hw.wangxiaoyin@hisilicon.com>
Signed-off-by: Wei Xu <xuwei5@hisilicon.com>