test: Add tests for IOMMU uclass

Add a set of tests for the IOMMU uclass.

Signed-off-by: Mark Kettenis <kettenis@openbsd.org>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/drivers/iommu/Makefile b/drivers/iommu/Makefile
index f1ceb10..af1c6bb 100644
--- a/drivers/iommu/Makefile
+++ b/drivers/iommu/Makefile
@@ -1,3 +1,5 @@
 # SPDX-License-Identifier: GPL-2.0+
 
 obj-$(CONFIG_IOMMU) += iommu-uclass.o
+
+obj-$(CONFIG_SANDBOX) += sandbox_iommu.o