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/configs/sandbox_spl_defconfig b/configs/sandbox_spl_defconfig
index b3274a9..25c974f 100644
--- a/configs/sandbox_spl_defconfig
+++ b/configs/sandbox_spl_defconfig
@@ -120,6 +120,7 @@
 CONFIG_DM_MAILBOX=y
 CONFIG_SANDBOX_MBOX=y
 CONFIG_MISC=y
+CONFIG_SOC_DEVICE=y
 CONFIG_CROS_EC=y
 CONFIG_CROS_EC_I2C=y
 CONFIG_CROS_EC_LPC=y