usb: host: ehci: Make use of dma_pool_zalloc() instead of dma_pool_alloc/memset()

Replacing dma_pool_alloc/memset() with dma_pool_zalloc()
to simplify the code.
Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20211018131645.434-1-caihuoqing@baidu.comSigned-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/usb/host/ehci-mem.c

@@ -73,10 +73,9 @@ static struct ehci_qh *ehci_qh_alloc (struct ehci_hcd *ehci, gfp_t flags)
 	if (!qh)
 		goto done;
 	qh->hw = (struct ehci_qh_hw *)
-		dma_pool_alloc(ehci->qh_pool, flags, &dma);
+		dma_pool_zalloc(ehci->qh_pool, flags, &dma);
 	if (!qh->hw)
 		goto fail;
-	memset(qh->hw, 0, sizeof *qh->hw);
 	qh->qh_dma = dma;
 	// INIT_LIST_HEAD (&qh->qh_list);
 	INIT_LIST_HEAD (&qh->qtd_list);