sandbox: pch: Add a test for the PCH uclass

This uclass currently has no tests. Add a sandbox driver and some simple
tests to provide basic coverage.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
[bmeng: Use "sandbox,pch" for the compatible string, for consistency]
Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
diff --git a/arch/sandbox/dts/test.dts b/arch/sandbox/dts/test.dts
index 1d011de..f014c56 100644
--- a/arch/sandbox/dts/test.dts
+++ b/arch/sandbox/dts/test.dts
@@ -407,6 +407,10 @@
 		compatible = "sandbox,mmc";
 	};
 
+	pch {
+		compatible = "sandbox,pch";
+	};
+
 	pci0: pci-controller0 {
 		compatible = "sandbox,pci";
 		device_type = "pci";