test: dm: virtio: Add test cases for virtio uclass

Now that we have a sandbox virtio transport driver, add some test
cases to test virtio uclass driver.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 71d1b39..6b54115 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -716,6 +716,14 @@
 	sandbox_tee {
 		compatible = "sandbox,tee";
 	};
+
+	sandbox_virtio1 {
+		compatible = "sandbox,virtio1";
+	};
+
+	sandbox_virtio2 {
+		compatible = "sandbox,virtio2";
+	};
 };
 
 #include "sandbox_pmic.dtsi"