ALSA: vx: Convert to the common vmalloc memalloc

The recent change (*) in the ALSA memalloc core allows us to drop the
special vmalloc-specific allocation and page handling.  This patch
coverts to the common code.
(*) 1fe7f397: ALSA: memalloc: Add vmalloc buffer allocation
                  support
    7e8edae3: ALSA: pcm: Handle special page mapping in the
                  default mmap handler

Since the driver requires the DMA32 allocation, it passes the
specially encoded device to snd_pcm_lib_preallocate_pages().

Link: https://lore.kernel.org/r/20191105151856.10785-16-tiwai@suse.deSigned-off-by: Takashi Iwai <tiwai@suse.de>

sound/drivers/vx/vx_pcm.c

@@ -778,8 +778,7 @@ static snd_pcm_uframes_t vx_pcm_playback_pointer(struct snd_pcm_substream *subs)
 static int vx_pcm_hw_params(struct snd_pcm_substream *subs,
 				     struct snd_pcm_hw_params *hw_params)
 {
-	return snd_pcm_lib_alloc_vmalloc_32_buffer
-					(subs, params_buffer_bytes(hw_params));
+	return snd_pcm_lib_malloc_pages(subs, params_buffer_bytes(hw_params));
 }
 
 /*
@@ -787,7 +786,7 @@ static int vx_pcm_hw_params(struct snd_pcm_substream *subs,
  */
 static int vx_pcm_hw_free(struct snd_pcm_substream *subs)
 {
-	return snd_pcm_lib_free_vmalloc_buffer(subs);
+	return snd_pcm_lib_free_pages(subs);
 }
 
 /*
@@ -867,7 +866,6 @@ static const struct snd_pcm_ops vx_pcm_playback_ops = {
 	.prepare =	vx_pcm_prepare,
 	.trigger =	vx_pcm_trigger,
 	.pointer =	vx_pcm_playback_pointer,
-	.page =		snd_pcm_lib_get_vmalloc_page,
 };
 
 
@@ -1088,7 +1086,6 @@ static const struct snd_pcm_ops vx_pcm_capture_ops = {
 	.prepare =	vx_pcm_prepare,
 	.trigger =	vx_pcm_trigger,
 	.pointer =	vx_pcm_capture_pointer,
-	.page =		snd_pcm_lib_get_vmalloc_page,
 };
 
 
@@ -1233,6 +1230,9 @@ int snd_vx_pcm_new(struct vx_core *chip)
 			snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_PLAYBACK, &vx_pcm_playback_ops);
 		if (ins)
 			snd_pcm_set_ops(pcm, SNDRV_PCM_STREAM_CAPTURE, &vx_pcm_capture_ops);
+		snd_pcm_lib_preallocate_pages_for_all(pcm, SNDRV_DMA_TYPE_VMALLOC,
+						      snd_dma_continuous_data(GFP_KERNEL | GFP_DMA32),
+						      0, 0);
 
 		pcm->private_data = chip;
 		pcm->private_free = snd_vx_pcm_free;