ARM: dma-mapping: Pass device to arm_iommu_create_mapping()

All users of ARM IOMMU mappings create them for a particular device, so
change the interface to accept the device rather than forcing a vague
indirection through a bus type. This prepares for making a similar
change to iommu_domain_alloc() itself.

Signed-off-by: Robin Murphy <robin.murphy@arm.com>