spi/bitbang: (cosmetic) simplify list manipulation

Use a proper list iterator instead of an open-coded loop and remove a
superfluous list head initialisation.
Signed-off-by: NGuennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: NGrant Likely <grant.likely@secretlab.ca>

drivers/spi/spi-bitbang.c

@@ -260,11 +260,11 @@ static void bitbang_work(struct work_struct *work)
 	struct spi_bitbang	*bitbang =
 		container_of(work, struct spi_bitbang, work);
 	unsigned long		flags;
+	struct spi_message	*m, *_m;
 
 	spin_lock_irqsave(&bitbang->lock, flags);
 	bitbang->busy = 1;
-	while (!list_empty(&bitbang->queue)) {
-		struct spi_message	*m;
+	list_for_each_entry_safe(m, _m, &bitbang->queue, queue) {
 		struct spi_device	*spi;
 		unsigned		nsecs;
 		struct spi_transfer	*t = NULL;
@@ -273,9 +273,7 @@ static void bitbang_work(struct work_struct *work)
 		int			status;
 		int			do_setup = -1;
 
-		m = container_of(bitbang->queue.next, struct spi_message,
-				queue);
-		list_del_init(&m->queue);
+		list_del(&m->queue);
 		spin_unlock_irqrestore(&bitbang->lock, flags);
 
 		/* FIXME this is made-up ... the correct value is known to