clearfog: Use a custom DTS file

It was necessary to use a differently named DTS file, unfortunately, and
that also led to an incompatible change in the bootloader. A full flash
is therefore required. I wasn't able to use the same file name if I want
to avoid duplication by just including the original DTS board file, and
adding some post hooks for copying just sounded ugly.

Change-Id: Ia8c11a3f43033a18ed2a8dbae996512e38358367
diff --git a/board/czechlight/clearfog/czechlight-clearfog.dts b/board/czechlight/clearfog/czechlight-clearfog.dts
new file mode 100644
index 0000000..8e48f49
--- /dev/null
+++ b/board/czechlight/clearfog/czechlight-clearfog.dts
@@ -0,0 +1 @@
+#include "armada-388-clearfog-base.dts"