Revert "sandbox: Disable I2C emulators in SPL"

With recent changes this can be supported again. Add it back.

This reverts commit d85f2c4f2970d0ec2f5f075de734afd11200d153.

Signed-off-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/sandbox/dts/sandbox.dtsi b/arch/sandbox/dts/sandbox.dtsi
index 5bf8445..69d7d30 100644
--- a/arch/sandbox/dts/sandbox.dtsi
+++ b/arch/sandbox/dts/sandbox.dtsi
@@ -264,14 +264,10 @@
 		stringarray = "pre-proper";
 	};
 
-	test-bus {
-		compatible = "simple-bus";
+	spl-test7 {
 		u-boot,dm-spl;
-		spl-test7 {
-			u-boot,dm-spl;
-			compatible = "sandbox,spl-test";
-			stringarray = "spl";
-		};
+		compatible = "sandbox,spl-test";
+		stringarray = "spl";
 	};
 
 	square {