ALSA: hda: beep: Simplify keep-power-at-enable behavior

The recent fix for IDT codecs to keep the power up while the beep is
enabled can be better integrated into the beep helper code.
This patch cleans up the code with refactoring.

Fixes: 414d38ba ("ALSA: hda/sigmatel: Keep power up while beep is enabled")
Link: https://lore.kernel.org/r/20220906092306.26183-1-tiwai@suse.de


Signed-off-by: Takashi Iwai <tiwai@suse.de>