dma: bcm6348: check if driver is enabled before send/recv

This patch prevents errors when running tftpput.

Signed-off-by: Álvaro Fernández Rojas <noltari@gmail.com>
diff --git a/drivers/dma/bcm6348-iudma.c b/drivers/dma/bcm6348-iudma.c
index 1d3c192..e7bd1b2 100644
--- a/drivers/dma/bcm6348-iudma.c
+++ b/drivers/dma/bcm6348-iudma.c
@@ -324,6 +324,9 @@
 	struct bcm6348_dma_desc *dma_desc = dma_desc = ch_priv->dma_ring;
 	int ret;
 
+	if (!ch_priv->running)
+		return -EINVAL;
+
 	/* get dma ring descriptor address */
 	dma_desc += ch_priv->desc_id;
 
@@ -369,6 +372,9 @@
 	struct bcm6348_dma_desc *dma_desc;
 	uint16_t status;
 
+	if (!ch_priv->running)
+                return -EINVAL;
+
 	/* flush cache */
 	bcm6348_iudma_fdc(src, len);