ALSA: pci/ctxfi: fix kernel-doc warnings

Fix W=1 warnings. The files contain formatting that isn't kernel-doc.
Signed-off-by: Pierre-Louis Bossart <pierre-louis.bossart@linux.intel.com>
Link: https://lore.kernel.org/r/20200702193604.169059-10-pierre-louis.bossart@linux.intel.comSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/ctxfi/cthardware.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (C) 2008, Creative Technology Ltd. All Rights Reserved.
  *
  * @File	cthardware.c

sound/pci/ctxfi/cthw20k1.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (C) 2008, Creative Technology Ltd. All Rights Reserved.
  *
  * @File	cthw20k1.c

sound/pci/ctxfi/cthw20k2.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (C) 2008, Creative Technology Ltd. All Rights Reserved.
  *
  * @File	cthw20k2.c

sound/pci/ctxfi/ctimap.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (C) 2008, Creative Technology Ltd. All Rights Reserved.
  *
  * @File	ctimap.c

sound/pci/ctxfi/ctmixer.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (C) 2008, Creative Technology Ltd. All Rights Reserved.
  *
  * @File	ctmixer.c

sound/pci/ctxfi/ctpcm.c

 // SPDX-License-Identifier: GPL-2.0-only
-/**
+/*
  * Copyright (C) 2008, Creative Technology Ltd. All Rights Reserved.
  *
  * @File	ctpcm.c