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: Prasad Joshi <prasadjoshi.linux@gmail.com>
Signed-off-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
diff --git a/sound/soc/spear/spear_pcm.c b/sound/soc/spear/spear_pcm.c
index 97c2cac..8c7f237 100644
--- a/sound/soc/spear/spear_pcm.c
+++ b/sound/soc/spear/spear_pcm.c
@@ -138,7 +138,7 @@
 			continue;
 
 		buf = &substream->dma_buffer;
-		if (!buf && !buf->area)
+		if (!buf || !buf->area)
 			continue;
 
 		dma_free_writecombine(pcm->card->dev, buf->bytes,