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/drivers/board/Makefile b/drivers/board/Makefile
index 12dd203..2224338 100644
--- a/drivers/board/Makefile
+++ b/drivers/board/Makefile
@@ -4,3 +4,4 @@
 # Mario Six,  Guntermann & Drunck GmbH, mario.six@gdsys.cc
 obj-$(CONFIG_BOARD) += board-uclass.o
 obj-$(CONFIG_BOARD_GAZERBEAM) += gazerbeam.o
+obj-$(CONFIG_BOARD_SANDBOX) += sandbox.o