leds: simatic-ipc-leds-gpio: Fix comment style in SPDX header

This was found with giving the file to checkpatch.
Signed-off-by: Henning Schild <henning.schild@siemens.com>
Link: https://lore.kernel.org/r/20230706161040.21152-3-henning.schild@siemens.comSigned-off-by: Lee Jones <lee@kernel.org>

drivers/leds/simple/simatic-ipc-leds-gpio.h

-// SPDX-License-Identifier: GPL-2.0
+/* SPDX-License-Identifier: GPL-2.0 */
 /*
  * Siemens SIMATIC IPC driver for GPIO based LEDs
  *