iommu: Add set_platform_dma_ops callbacks

For those IOMMU drivers that don't provide default domain support, add an
implementation of set_platform_dma_ops callback so that the IOMMU core
could return the DMA control to platform DMA ops. At the same time, with
the set_platform_dma_ops implemented, there is no need for detach_dev.
Remove it to avoid dead code.

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Link: https://lore.kernel.org/r/20230110025408.667767-4-baolu.lu@linux.intel.com
Signed-off-by: Joerg Roedel <jroedel@suse.de>