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/configs/sandbox_noinst_defconfig b/configs/sandbox_noinst_defconfig
index 238604f..ab37849 100644
--- a/configs/sandbox_noinst_defconfig
+++ b/configs/sandbox_noinst_defconfig
@@ -128,6 +128,7 @@
 CONFIG_I2C_ARB_GPIO_CHALLENGE=y
 CONFIG_CROS_EC_KEYB=y
 CONFIG_I8042_KEYB=y
+CONFIG_IOMMU=y
 CONFIG_LED=y
 CONFIG_LED_BLINK=y
 CONFIG_LED_GPIO=y