gpio: max730x: don't use kernel-doc marker for regular comment

Use a common C comment (/*) instead of kernel-doc notation to prevent
warnings from scripts/kernel-doc.

gpio-max730x.c:3: warning: This comment starts with '/**', but isn't a kernel-doc comment. Refer Documentation/doc-guide/kernel-doc.rst
gpio-max730x.c:3: warning: missing initial short description on line:
 * Copyright (C) 2006 Juergen Beisert, Pengutronix
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/gpio-max730x.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (C) 2006 Juergen Beisert, Pengutronix
  * Copyright (C) 2008 Guennadi Liakhovetski, Pengutronix
  * Copyright (C) 2009 Wolfram Sang, Pengutronix