list.h: Add list_splice_tail() and list_splice_tail_init()

If you are using linked lists for queues list_splice() will not do what
you would expect even if you use the elements passed reversed. We need
to handle these differently. We add list_splice_tail() and
list_splice_tail_init().

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Signed-off-by: Luis R. Rodriguez <lrodriguez@atheros.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/drivers/dma/ioat_dma.c b/drivers/dma/ioat_dma.c
index a52156e..bc8c6e3 100644
--- a/drivers/dma/ioat_dma.c
+++ b/drivers/dma/ioat_dma.c
@@ -551,7 +551,7 @@
 	/* write address into NextDescriptor field of last desc in chain */
 	to_ioat_desc(ioat_chan->used_desc.prev)->hw->next =
 							first->async_tx.phys;
-	__list_splice(&new_chain, ioat_chan->used_desc.prev);
+	list_splice_tail(&new_chain, &ioat_chan->used_desc);
 
 	ioat_chan->dmacount += desc_count;
 	ioat_chan->pending += desc_count;