ALSA: control: Minor optimization for SNDRV_CTL_IOCTL_POWER_STATE

Long long time ago, before the proper PM framework was introduced, it
was still possible to reach SNDRV_CTL_IOCTL_POWER ioctl during the
power off state.  This ioctl existed as a main control for the suspend
resume state in the past, but the feature was already dropped along
with the standard PM framework.  Now the read part,
SNDRV_IOCTL_POWER_STATE ioctl, returns practically always D0, and we
can do some minor optimization there.

Reviewed-by: Jaroslav Kysela <perex@perex.cz>
Link: https://lore.kernel.org/r/20210523090920.15345-5-tiwai@suse.de


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