dmaengine: use kmem_cache_zalloc instead of kmem_cache_alloc/memset

Using kmem_cache_zalloc() instead of kmem_cache_alloc() and memset().

spatch with a semantic match is used to found this problem.
(http://coccinelle.lip6.fr/)
Signed-off-by: Wei Yongjun <yongjun_wei@trendmicro.com.cn>
Signed-off-by: Vinod Koul <vinod.koul@linux.intel.com>

drivers/dma/ioat/dma_v2.c

@@ -434,12 +434,11 @@ static struct ioat_ring_ent *ioat2_alloc_ring_ent(struct dma_chan *chan, gfp_t f
 		return NULL;
 	memset(hw, 0, sizeof(*hw));
 
-	desc = kmem_cache_alloc(ioat2_cache, flags);
+	desc = kmem_cache_zalloc(ioat2_cache, flags);
 	if (!desc) {
 		pci_pool_free(dma->dma_pool, hw, phys);
 		return NULL;
 	}
-	memset(desc, 0, sizeof(*desc));
 
 	dma_async_tx_descriptor_init(&desc->txd, chan);
 	desc->txd.tx_submit = ioat2_tx_submit_unlock;