iommu/rockchip: Drop IOVA cookie management

The core code bakes its own cookies now.

Tested-by: Heiko Stuebner <heiko@sntech.de>
Acked-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Robin Murphy <robin.murphy@arm.com>
Link: https://lore.kernel.org/r/aff51e2da1e431987ae5fdafa62a6a7c4bd042dc.1628682048.git.robin.murphy@arm.com


Signed-off-by: Joerg Roedel <jroedel@suse.de>