ALSA: pcm - Export snd_pcm_lib_default_mmap() helper

Export the default mmap function, snd_pcm_lib_default_mmap().
The upcoming non-snooping support in HD-audio driver will use this
to override the mmap method.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/core/pcm_native.c b/sound/core/pcm_native.c
index 1c6be91..b4bf4a4 100644
--- a/sound/core/pcm_native.c
+++ b/sound/core/pcm_native.c
@@ -3156,8 +3156,8 @@
 /*
  * mmap the DMA buffer on RAM
  */
-static int snd_pcm_default_mmap(struct snd_pcm_substream *substream,
-				struct vm_area_struct *area)
+int snd_pcm_lib_default_mmap(struct snd_pcm_substream *substream,
+			     struct vm_area_struct *area)
 {
 	area->vm_flags |= VM_RESERVED;
 #ifdef ARCH_HAS_DMA_MMAP_COHERENT
@@ -3177,6 +3177,7 @@
 	area->vm_ops = &snd_pcm_vm_ops_data_fault;
 	return 0;
 }
+EXPORT_SYMBOL_GPL(snd_pcm_lib_default_mmap);
 
 /*
  * mmap the DMA buffer on I/O memory area
@@ -3242,7 +3243,7 @@
 	if (substream->ops->mmap)
 		err = substream->ops->mmap(substream, area);
 	else
-		err = snd_pcm_default_mmap(substream, area);
+		err = snd_pcm_lib_default_mmap(substream, area);
 	if (!err)
 		atomic_inc(&substream->mmap_count);
 	return err;