[ALSA] Fix Makefile of cs5535audio

Use ifeq instead of ifdef in Makefile to make the maintenance of
out-of-kernel tree easier.
Signed-off-by: NTakashi Iwai <tiwai@suse.de>
Signed-off-by: NJaroslav Kysela <perex@suse.cz>

sound/pci/cs5535audio/Makefile

@@ -4,7 +4,7 @@
 
 snd-cs5535audio-objs := cs5535audio.o cs5535audio_pcm.o
 
-ifdef CONFIG_PM
+ifeq ($(CONFIG_PM),y)
 snd-cs5535audio-objs += cs5535audio_pm.o
 endif