ASoC: spear: correct the check for NULL dma_buffer pointer

The if condition
	if (!buf && !buf->area)

checks if the buf pointer is NULL and then dereferences it again to
check if the buffer area is NULL, resulting in possible NULL
dereference.
Signed-off-by: NPrasad Joshi <prasadjoshi.linux@gmail.com>
Signed-off-by: NMark Brown <broonie@opensource.wolfsonmicro.com>

sound/soc/spear/spear_pcm.c

@@ -138,7 +138,7 @@ static void spear_pcm_free(struct snd_pcm *pcm)
 			continue;
 
 		buf = &substream->dma_buffer;
-		if (!buf && !buf->area)
+		if (!buf || !buf->area)
 			continue;
 
 		dma_free_writecombine(pcm->card->dev, buf->bytes,