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>