[ALSA] ac97 - Suppress power-saving mode on non-supporting drivers

Don't enable power-saving mode on drivers that don't support
it.  The supporting drivers set AC97_SCAP_POWER_SAVE to scaps
at creation of ac97 instance.
Currently enable on the following drivers: intel8x0, intel8x0m,
atiixp, atiixp-modem, via82xx and via82xx-modem.
Also, a bit clean up of power-saving stuff:
- Don't create an own workq
- Remove superfluous ifdefs

Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Jaroslav Kysela <perex@suse.cz>
diff --git a/sound/pci/intel8x0.c b/sound/pci/intel8x0.c
index 28d5d9d..f8aef13 100644
--- a/sound/pci/intel8x0.c
+++ b/sound/pci/intel8x0.c
@@ -2057,7 +2057,7 @@
 	memset(&ac97, 0, sizeof(ac97));
 	ac97.private_data = chip;
 	ac97.private_free = snd_intel8x0_mixer_free_ac97;
-	ac97.scaps = AC97_SCAP_SKIP_MODEM;
+	ac97.scaps = AC97_SCAP_SKIP_MODEM | AC97_SCAP_POWER_SAVE;
 	if (chip->xbox)
 		ac97.scaps |= AC97_SCAP_DETECT_BY_VENDOR;
 	if (chip->device_type != DEVICE_ALI) {