iommu/amd: Rip out old queue flushing code

The queue flushing is pretty inefficient when it flushes the
queues for all cpus at once. Further it flushes all domains
from all IOMMUs for all CPUs, which is overkill as well.

Rip it out to make room for something more efficient.

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