ALSA: pcm: Define dummy snd_pcm_suspend() for CONFIG_PM=n

... so that the driver can avoid ifdef's for the dead PM callbacks.
The compiler should optimize them out in anyway.
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>

include/sound/pcm.h

@@ -570,6 +570,15 @@ int snd_pcm_stop_xrun(struct snd_pcm_substream *substream);
 #ifdef CONFIG_PM
 int snd_pcm_suspend(struct snd_pcm_substream *substream);
 int snd_pcm_suspend_all(struct snd_pcm *pcm);
+#else
+static inline int snd_pcm_suspend(struct snd_pcm_substream *substream)
+{
+	return 0;
+}
+static inline int snd_pcm_suspend_all(struct snd_pcm *pcm)
+{
+	return 0;
+}
 #endif
 int snd_pcm_kernel_ioctl(struct snd_pcm_substream *substream, unsigned int cmd, void *arg);
 int snd_pcm_open_substream(struct snd_pcm *pcm, int stream, struct file *file,