test: Add tests for board uclass

Add tests for the new board uclass.

Reviewed-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Mario Six <mario.six@gdsys.cc>
diff --git a/configs/sandbox_flattree_defconfig b/configs/sandbox_flattree_defconfig
index 618d646..1d3dd9f 100644
--- a/configs/sandbox_flattree_defconfig
+++ b/configs/sandbox_flattree_defconfig
@@ -70,6 +70,8 @@
 CONFIG_DM_DEMO=y
 CONFIG_DM_DEMO_SIMPLE=y
 CONFIG_DM_DEMO_SHAPE=y
+CONFIG_BOARD=y
+CONFIG_BOARD_SANDBOX=y
 CONFIG_PM8916_GPIO=y
 CONFIG_SANDBOX_GPIO=y
 CONFIG_DM_I2C_COMPAT=y