staging: hikey9xx: phy-hi3670-usb3: change some DT properties

Do some changes at the DT properties in order to make it
follow the phy-hi3660-usb3 example and to simplify
usb3-phy-tx-vboost-lvl name.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/da128b9943bcb6a3d44a9512cedc7fa7a4aedee6.1600338981.git.mchehab+huawei@kernel.org


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