dmaengine: cleanup with list_first_entry_or_null()

The combo of list_empty() check and return list_first_entry()
can be replaced with list_first_entry_or_null().

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>
diff --git a/drivers/dma/ste_dma40.c b/drivers/dma/ste_dma40.c
index 8b18e44..e43d2bb 100644
--- a/drivers/dma/ste_dma40.c
+++ b/drivers/dma/ste_dma40.c
@@ -941,15 +941,7 @@
 
 static struct d40_desc *d40_first_active_get(struct d40_chan *d40c)
 {
-	struct d40_desc *d;
-
-	if (list_empty(&d40c->active))
-		return NULL;
-
-	d = list_first_entry(&d40c->active,
-			     struct d40_desc,
-			     node);
-	return d;
+	return list_first_entry_or_null(&d40c->active, struct d40_desc, node);
 }
 
 /* remove desc from current queue and add it to the pending_queue */
@@ -962,36 +954,18 @@
 
 static struct d40_desc *d40_first_pending(struct d40_chan *d40c)
 {
-	struct d40_desc *d;
-
-	if (list_empty(&d40c->pending_queue))
-		return NULL;
-
-	d = list_first_entry(&d40c->pending_queue,
-			     struct d40_desc,
-			     node);
-	return d;
+	return list_first_entry_or_null(&d40c->pending_queue, struct d40_desc,
+					node);
 }
 
 static struct d40_desc *d40_first_queued(struct d40_chan *d40c)
 {
-	struct d40_desc *d;
-
-	if (list_empty(&d40c->queue))
-		return NULL;
-
-	d = list_first_entry(&d40c->queue,
-			     struct d40_desc,
-			     node);
-	return d;
+	return list_first_entry_or_null(&d40c->queue, struct d40_desc, node);
 }
 
 static struct d40_desc *d40_first_done(struct d40_chan *d40c)
 {
-	if (list_empty(&d40c->done))
-		return NULL;
-
-	return list_first_entry(&d40c->done, struct d40_desc, node);
+	return list_first_entry_or_null(&d40c->done, struct d40_desc, node);
 }
 
 static int d40_psize_2_burst_size(bool is_log, int psize)