iommu: Change iommu driver to call add_device_to_group trace event

Change iommu driver to call add_device_to_group trace event. This iommu_group
class event can be enabled to trigger when devices get added to an iommu group.
Trace information includes iommu group id and device name.

Testing:
The following is trace is generated when intel-iommu driver adds devices to
to iommu groups during boot-time during its initialization:

       swapper/0-1     [003] ....     1.854793: add_device_to_group: IOMMU: groupID=0 device=0000:00:00.0
       swapper/0-1     [003] ....     1.854797: add_device_to_group: IOMMU: groupID=1 device=0000:00:02.0

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

drivers/iommu/iommu.c

@@ -364,6 +364,8 @@ rename:
 	/* Notify any listeners about change to group. */
 	blocking_notifier_call_chain(&group->notifier,
 				     IOMMU_GROUP_NOTIFY_ADD_DEVICE, dev);
+
+	trace_add_device_to_group(group->id, dev);
 	return 0;
 }
 EXPORT_SYMBOL_GPL(iommu_group_add_device);