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>