USB: musb: Use the correct style for SPDX License Identifier

This patch corrects the SPDX License Identifier style in
header files related to USB Dual Role (OTG-ready) Controller Drivers.
For C header files Documentation/process/license-rules.rst
mandates C-like comments (opposed to C source files where
C++ style should be used).

Changes made by using a script provided by Joe Perches here:
https://lkml.org/lkml/2019/2/7/46.
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Nishad Kamdar <nishadkamdar@gmail.com>
Link: https://lore.kernel.org/r/20200404104952.GA6575@nishadSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/musb/davinci.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright (C) 2005-2006 by Texas Instruments
  */

drivers/usb/musb/musb_core.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * MUSB OTG driver defines
  *

drivers/usb/musb/musb_debug.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * MUSB OTG driver debug defines
  *

drivers/usb/musb/musb_dma.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * MUSB OTG driver DMA controller abstraction
  *

drivers/usb/musb/musb_gadget.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * MUSB OTG driver peripheral defines
  *

drivers/usb/musb/musb_host.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * MUSB OTG driver host defines
  *

drivers/usb/musb/musb_io.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * MUSB OTG driver register I/O
  *

drivers/usb/musb/musb_regs.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * MUSB OTG driver register defines
  *

drivers/usb/musb/musb_trace.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * musb_trace.h - MUSB Controller Trace Support
  *

drivers/usb/musb/omap2430.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Copyright (C) 2005-2006 by Texas Instruments
  */

drivers/usb/musb/tusb6010.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Definitions for TUSB6010 USB 2.0 OTG Dual Role controller
  *