dt-bindings: misc: Add bindings for HiSilicon usb hub and data role switch...

dt-bindings: misc: Add bindings for HiSilicon usb hub and data role switch functionality on HiKey960

This patch adds binding documentation to support usb hub and usb
data role switch of Hisilicon HiKey960 Board.

Cc: Sergei Shtylyov <sergei.shtylyov@cogentembedded.com>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Binghui Wang <wangbinghui@hisilicon.com>
Signed-off-by: Yu Chen <chenyu56@huawei.com>