ALSA: hda/sigmatel - remove unused variable 'stac9200_core_init'

sound/pci/hda/patch_sigmatel.c:981:30: warning:
 stac9200_core_init defined but not used [-Wunused-const-variable=]

It is never used, so can be removed.

Reported-by: Hulk Robot <hulkci@huawei.com>
Signed-off-by: YueHaibing <yuehaibing@huawei.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>