[ALSA] no need to check pointers passed to vfree() for NULL

Modules: Digigram VX core,USB generic driver

There's no need to check pointers passed to vfree() for NULL.

Signed-off-by: Jesper Juhl <jesper.juhl@gmail.com>
Signed-off-by: Takashi Iwai <tiwai@suse.de>
diff --git a/sound/usb/usbaudio.c b/sound/usb/usbaudio.c
index 7b1b9f2..039f27d 100644
--- a/sound/usb/usbaudio.c
+++ b/sound/usb/usbaudio.c
@@ -720,10 +720,9 @@
 static int snd_pcm_free_vmalloc_buffer(struct snd_pcm_substream *subs)
 {
 	struct snd_pcm_runtime *runtime = subs->runtime;
-	if (runtime->dma_area) {
-		vfree(runtime->dma_area);
-		runtime->dma_area = NULL;
-	}
+
+	vfree(runtime->dma_area);
+	runtime->dma_area = NULL;
 	return 0;
 }