misc: hisi_hikey_usb: add support for Hikey 970

The HiKey 970 board is similar to Hikey 960 with regards
to its USB configutation: it also relies on a USB HUB
that is used when DWC3 is at host mode.

However, it requires a few extra DT settings, as it
uses a voltage regulator and GPIO reset pin.

Add support for them.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/62843df9927b4d8dac5dc7c4a189567fa52ab2bb.1599717402.git.mchehab+huawei@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>