ALSA: pcm - Call pgprot_noncached() for vmalloc'ed buffers

pgprot_noncached() can be set for vmalloc'ed buffers safely, and we'd
need non-cached behavior more or less, even for the intermediate ring-
buffers.

Now snd_pcm_lib_mmap_vmalloc() is added as the common PCM mmap callback
that is coupled with snd_pcm_lib_alloc_vmalloc_buffer() & co.

Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 4ada98e..b8e0b8f 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -1997,6 +1997,7 @@
 	.trigger =	snd_usb_pcm_playback_trigger,
 	.pointer =	snd_usb_pcm_pointer,
 	.page =		snd_pcm_lib_get_vmalloc_page,
+	.mmap =		snd_pcm_lib_mmap_vmalloc,
 };
 
 static struct snd_pcm_ops snd_usb_capture_ops = {
@@ -2009,6 +2010,7 @@
 	.trigger =	snd_usb_pcm_capture_trigger,
 	.pointer =	snd_usb_pcm_pointer,
 	.page =		snd_pcm_lib_get_vmalloc_page,
+	.mmap =		snd_pcm_lib_mmap_vmalloc,
 };