ALSA: hda - Export snd_hda_lock_devices()

It's a preliminary work for the vga-switcher support.
Export the function to do pseudo-lock for the sound card to be used
in other places.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/pci/hda/hda_codec.h b/sound/pci/hda/hda_codec.h
index 29a311b..be91cdb 100644
--- a/sound/pci/hda/hda_codec.h
+++ b/sound/pci/hda/hda_codec.h
@@ -1020,6 +1020,9 @@
 				    unsigned int power_state,
 				    bool eapd_workaround);
 
+int snd_hda_lock_devices(struct hda_bus *bus);
+void snd_hda_unlock_devices(struct hda_bus *bus);
+
 /*
  * power management
  */