Input: wm831x-on - source file headers are not good candidates for kernel-doc

Fixes the following W=1 kernel build warning(s):

 drivers/input/misc/wm831x-on.c:30: warning: cannot understand function prototype: 'struct wm831x_on '
Signed-off-by: Lee Jones <lee.jones@linaro.org>
Acked-by: Richard Fitzgerald <rf@opensource.cirrus.com>
Link: https://lore.kernel.org/r/20201112110204.2083435-10-lee.jones@linaro.orgSigned-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/misc/wm831x-on.c

-/**
+/*
  * wm831x-on.c - WM831X ON pin driver
  *
  * Copyright (C) 2009 Wolfson Microelectronics plc