usb: dwc3: ulpi: File headers are not doc headers

Demote ulpi.c's file header to a standard comment block.

Fixes the following W=1 build warning:

 drivers/usb/dwc3/ulpi.c:18: warning: Function parameter or member 'a' not described in 'DWC3_ULPI_ADDR'

Cc: Felipe Balbi <balbi@kernel.org>
Cc: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Link: https://lore.kernel.org/r/20200702144625.2533530-7-lee.jones@linaro.orgSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/ulpi.c

 // SPDX-License-Identifier: GPL-2.0
-/**
+/*
  * ulpi.c - DesignWare USB3 Controller's ULPI PHY interface
  *
  * Copyright (C) 2015 Intel Corporation