ALSA: platform: Check CONFIG_PM_SLEEP instead of CONFIG_PM

When CONFIG_PM is set but CONFIG_PM_SLEEP is unset,
SIMPLE_DEV_PM_OPS() ignores the given functions, and this leads to
compile warnings.

For avoiding this, simply check CONFIG_PM_SLEEP instead of CONFIG_PM.

Reported-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/drivers/aloop.c b/sound/drivers/aloop.c
index 1128b35..5a34355 100644
--- a/sound/drivers/aloop.c
+++ b/sound/drivers/aloop.c
@@ -1176,7 +1176,7 @@
 	return 0;
 }
 
-#ifdef CONFIG_PM
+#ifdef CONFIG_PM_SLEEP
 static int loopback_suspend(struct device *pdev)
 {
 	struct snd_card *card = dev_get_drvdata(pdev);