ALSA: hda - Add pcm_mmap_prepare op.

Adding this op allows the X86 specific mmap operation to help in
hda_intel without needing a CONFIG_X86 in future non-PCI hda drivers.

Signed-off-by: Dylan Reid <dgreid@chromium.org>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_priv.h b/sound/pci/hda/hda_priv.h
index 10bcec1..edbe2eb 100644
--- a/sound/pci/hda/hda_priv.h
+++ b/sound/pci/hda/hda_priv.h
@@ -309,6 +309,8 @@
 				     size_t size);
 	int (*substream_free_pages)(struct azx *chip,
 				    struct snd_pcm_substream *substream);
+	void (*pcm_mmap_prepare)(struct snd_pcm_substream *substream,
+				 struct vm_area_struct *area);
 };
 
 struct azx_pcm {