dm: sandbox: Add a board for sandbox without CONFIG_BLK

While the driver-model block device support is in progress, it is useful to
build sandbox both with and without CONFIG_BLK. Add a separate board for
the latter.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/sandbox/MAINTAINERS b/board/sandbox/MAINTAINERS
index 10d88a2..f5db773 100644
--- a/board/sandbox/MAINTAINERS
+++ b/board/sandbox/MAINTAINERS
@@ -4,3 +4,10 @@
 F:	board/sandbox/
 F:	include/configs/sandbox.h
 F:	configs/sandbox_defconfig
+
+SANDBOX_NOBLK BOARD
+M:	Simon Glass <sjg@chromium.org>
+S:	Maintained
+F:	board/sandbox/
+F:	include/configs/sandbox.h
+F:	configs/sandbox_noblk_defconfig