usb: dwc3: Resolve kernel-doc warning for Xilinx DWC3 driver

The kernel-doc run gave a warning for Xilinx DWC3 driver:

drivers/usb/dwc3/dwc3-xilinx.c:27: warning: expecting prototype for
dwc3(). Prototype was for XLNX_USB_PHY_RST_EN() instead

Basically it was due to an extra '*' in line:2. This patch fixes the same.
Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Manish Narani <manish.narani@xilinx.com>
Link: https://lore.kernel.org/r/1617904448-74611-2-git-send-email-manish.narani@xilinx.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/dwc3/dwc3-xilinx.c

 // SPDX-License-Identifier: GPL-2.0
-/**
+/*
  * dwc3-xilinx.c - Xilinx DWC3 controller specific glue driver
  *
  * Authors: Manish Narani <manish.narani@xilinx.com>