AMD IOMMU: move TLB flushing to the map/unmap helper functions

This patch moves the invocation of the flushing functions to the
map/unmap helpers because its common code in all dma_ops relevant
mapping/unmapping code.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>