staging: hikey9xx: phy-hi3670-usb3: fix coding style

Address the issues reported by checkpatch --strict,
and add a SPDX tag.
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Link: https://lore.kernel.org/r/6b1f66068905b7d0a9a988c9d0bd4ebef19a6fc2.1600338981.git.mchehab+huawei@kernel.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>