iommu: Change iommu driver to call unmap trace event

Change iommu driver to call unmap trace event. This iommu_map_unmap class
event can be enabled to trigger when iommu unmap iommu ops is called. Trace
information includes iova, physical address (map event only), and size.

Testing:
Added trace calls to iommu_prepare_identity_map() for testing some of the
conditions that are hard to trigger. Here is the trace from the testing:

       swapper/0-1     [003] ....     1.854102: unmap: IOMMU: iova=0x00000000cb800000 size=0x400

Signed-off-by: Shuah Khan <shuah.kh@samsung.com>
Signed-off-by: Joerg Roedel <joro@8bytes.org>

drivers/iommu/iommu.c

@@ -892,6 +892,7 @@ size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova, size_t size)
 		unmapped += unmapped_page;
 	}
 
+	trace_unmap(iova, 0, size);
 	return unmapped;
 }
 EXPORT_SYMBOL_GPL(iommu_unmap);