[media] cx88: use correct pci drvdata type in cx88_audio_finidev()

We had set the pci drvdata in cx88_audio_initdev() as a type of
struct snd_card, so cx88_audio_finidev() should used it as the
same type too.

Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>