Revert "iommu/amd: Remove the leftover of bypass support"

This reverts commit 7a5dbf3a.

This commit not only removes the leftovers of bypass
support, it also mostly removes the checking of the return
value of the get_domain() function. This can lead to silent
data corruption bugs when a device is not attached to its
dma_ops domain and a DMA-API function is called for that
device.

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