thunderbolt: Use kmemdup instead of kzalloc and memcpy

Fixes coccicheck warning:
drivers/thunderbolt/dma_test.c:302:13-20: WARNING opportunity for kmemdup.
Signed-off-by: NTian Tao <tiantao6@hisilicon.com>
Signed-off-by: NMika Westerberg <mika.westerberg@linux.intel.com>

drivers/thunderbolt/dma_test.c

@@ -299,14 +299,12 @@ static int dma_test_submit_tx(struct dma_test *dt, size_t npackets)
 		tf->frame.size = 0; /* means 4096 */
 		tf->dma_test = dt;
 
-		tf->data = kzalloc(DMA_TEST_FRAME_SIZE, GFP_KERNEL);
+		tf->data = kmemdup(dma_test_pattern, DMA_TEST_FRAME_SIZE, GFP_KERNEL);
 		if (!tf->data) {
 			kfree(tf);
 			return -ENOMEM;
 		}
 
-		memcpy(tf->data, dma_test_pattern, DMA_TEST_FRAME_SIZE);
-
 		dma_addr = dma_map_single(dma_dev, tf->data, DMA_TEST_FRAME_SIZE,
 					  DMA_TO_DEVICE);
 		if (dma_mapping_error(dma_dev, dma_addr)) {