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

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

commit 20c7793069509e72a37859a9e58169a793aeed45 upstream.

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

Fixes: 1d24d288c707 ("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.de
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>