dev-arm: Store the IOMMU reference from within the SMMU::connect

Change-Id: I35718a71dc040ee4acad9eee2a07076ebb571304
Signed-off-by: Giacomo Travaglini <giacomo.travaglini@arm.com>
Reviewed-by: Ciro Santilli <ciro.santilli@arm.com>
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/20840
Reviewed-by: Andreas Sandberg <andreas.sandberg@arm.com>
Maintainer: Andreas Sandberg <andreas.sandberg@arm.com>
Tested-by: kokoro <noreply+kokoro@google.com>

src/dev/arm/SMMUv3.py

@@ -207,3 +207,7 @@ class SMMUv3(ClockedObject):
             sys.exit(1)
 
         self.slave_interfaces.append(slave_interface)
+
+        # Storing a reference to the smmu to be used when generating
+        # the binding in the device DTB.
+        device._iommu = self