iommu/dart: Use kmemdup instead of kzalloc and memcpy

Fix following coccicheck warning:
drivers/iommu/apple-dart.c:704:20-27: WARNING opportunity for kmemdup

Signed-off-by: Wan Jiabing <wanjiabing@vivo.com>
Acked-by: Sven Peter <sven@svenpeter.dev>
Reviewed-by: Alyssa Rosenzweig <alyssa@rosenzweig.io>
Link: https://lore.kernel.org/r/20211013063441.29888-1-wanjiabing@vivo.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>

Author: Wan Jiabing

drivers/iommu/apple-dart.c

@@ -702,13 +702,12 @@ static struct iommu_group *apple_dart_device_group(struct device *dev)
 	if (!group)
 		goto out;
 
-	group_master_cfg = kzalloc(sizeof(*group_master_cfg), GFP_KERNEL);
+	group_master_cfg = kmemdup(cfg, sizeof(*group_master_cfg), GFP_KERNEL);
 	if (!group_master_cfg) {
 		iommu_group_put(group);
 		goto out;
 	}
 
-	memcpy(group_master_cfg, cfg, sizeof(*group_master_cfg));
 	iommu_group_set_iommudata(group, group_master_cfg,
 		apple_dart_release_group);