This helps map DMA addresses back to physical addresses.
Signed-off-by: NTom St Denis <tom.stdenis@amd.com>
Reviewed-by: NChristian König <christian.koenig@amd.com>
Signed-off-by: NAlex Deucher <alexander.deucher@amd.com>

(v2):  Added tracepoints for USERPTR, SG mappings, and
     SWIOTBL mappings.  Reformatted trace call perform
     PCI decoding internal to the trace.

(v3):  Add unmap tracepoints as well

(v4):  Move traces into separate functions