staging: comedi: comedi_usb.h: SPDX License Identifier is added in the first line

SPDX License Identifier is added in form of a comment.
Signed-off-by: Bhanusree Pola <bhanusreemahesh@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/comedi/comedi_usb.h

-// SPDX-License-Identifier: GPL-2.0+
-/*
- * comedi_usb.h
+/* SPDX-License-Identifier: GPL-2.0+ */
+/* comedi_usb.h
  * header file for USB Comedi drivers
  *
  * COMEDI - Linux Control and Measurement Device Interface