ALSA: hda/sigmatel: Fix unused variable warning for beep power change

The newly added stac_check_power_status() caused a compile warning
when CONFIG_SND_HDA_INPUT_BEEP is disabled.  Fix it.

Fixes: 414d38ba ("ALSA: hda/sigmatel: Keep power up while beep is enabled")
Reported-by: kernel test robot <lkp@intel.com>
Link: https://lore.kernel.org/r/20220905130630.2845-1-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/pci/hda/patch_sigmatel.c

@@ -4447,7 +4447,9 @@ static int stac_suspend(struct hda_codec *codec)
 
 static int stac_check_power_status(struct hda_codec *codec, hda_nid_t nid)
 {
+#ifdef CONFIG_SND_HDA_INPUT_BEEP
 	struct sigmatel_spec *spec = codec->spec;
+#endif
 	int ret = snd_hda_gen_check_power_status(codec, nid);
 
 #ifdef CONFIG_SND_HDA_INPUT_BEEP