ALSA: ac97: Fix double free of ac97_codec_device

put_device will call ac97_codec_release to free
ac97_codec_device and other resources, so remove the kfree
and other redundant code.

Fixes: 74426fbf

 ("ALSA: ac97: add an ac97 bus")
Signed-off-by: Ding Xiang <dingxiang@cmss.chinamobile.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>