test: Add tests for SOC uclass

Add a sandbox SOC driver, and some tests for the SOC uclass.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Dave Gerlach <d-gerlach@ti.com>
diff --git a/drivers/soc/Makefile b/drivers/soc/Makefile
index 1c09a84..649e92b 100644
--- a/drivers/soc/Makefile
+++ b/drivers/soc/Makefile
@@ -4,3 +4,4 @@
 
 obj-$(CONFIG_SOC_TI) += ti/
 obj-$(CONFIG_SOC_DEVICE) += soc-uclass.o
+obj-$(CONFIG_SANDBOX) += soc_sandbox.o