ALSA: Make snd_pcm_debug_name usable outside pcm_lib

Formatting a PCM name is useful for module debug too.
Add snd_prefix when making function public.

[minor coding-style fixes by tiwai]

Signed-off-by: Eliot Blennerhassett <eblennerhassett@audioscience.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/include/sound/pcm.h b/include/sound/pcm.h
index e1bad11..ccf3a6e 100644
--- a/include/sound/pcm.h
+++ b/include/sound/pcm.h
@@ -507,6 +507,18 @@
 void snd_pcm_vma_notify_data(void *client, void *data);
 int snd_pcm_mmap_data(struct snd_pcm_substream *substream, struct file *file, struct vm_area_struct *area);
 
+
+#ifdef CONFIG_SND_DEBUG
+void snd_pcm_debug_name(struct snd_pcm_substream *substream,
+			   char *name, size_t len);
+#else
+static inline void
+snd_pcm_debug_name(struct snd_pcm_substream *substream, char *buf, size_t size)
+{
+	*buf = 0;
+}
+#endif
+
 /*
  *  PCM library
  */