dmaengine: ioatdma: Use dma_pool_zalloc

Dma_pool_zalloc combines dma_pool_alloc and memset 0.  The semantic patch
that makes this transformation is as follows: (http://coccinelle.lip6.fr/)

// <smpl>
@@
expression d,e;
statement S;
@@

        d =
-            dma_pool_alloc
+            dma_pool_zalloc
             (...);
        if (!d) S
-       memset(d, 0, sizeof(*d));
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Vinod Koul <vinod.koul@intel.com>

drivers/dma/ioat/init.c

@@ -690,12 +690,11 @@ static int ioat_alloc_chan_resources(struct dma_chan *c)
 	/* allocate a completion writeback area */
 	/* doing 2 32bit writes to mmio since 1 64b write doesn't work */
 	ioat_chan->completion =
-		dma_pool_alloc(ioat_chan->ioat_dma->completion_pool,
-			       GFP_KERNEL, &ioat_chan->completion_dma);
+		dma_pool_zalloc(ioat_chan->ioat_dma->completion_pool,
+				GFP_KERNEL, &ioat_chan->completion_dma);
 	if (!ioat_chan->completion)
 		return -ENOMEM;
 
-	memset(ioat_chan->completion, 0, sizeof(*ioat_chan->completion));
 	writel(((u64)ioat_chan->completion_dma) & 0x00000000FFFFFFFF,
 	       ioat_chan->reg_base + IOAT_CHANCMP_OFFSET_LOW);
 	writel(((u64)ioat_chan->completion_dma) >> 32,