Add DTS files for the SDN ROADM models

Buildroot is smart enough to work with .dtsi includes as well, yay for
them.

Change-Id: I5a78625dc9f4883a39e3001c66edcd5dc6259434
diff --git a/board/czechlight/clearfog/sdn-roadm-line-clearfog.dts b/board/czechlight/clearfog/sdn-roadm-line-clearfog.dts
new file mode 100644
index 0000000..39f5e7a
--- /dev/null
+++ b/board/czechlight/clearfog/sdn-roadm-line-clearfog.dts
@@ -0,0 +1 @@
+#include "sdn-roadm-clearfog.dtsi"