Images for Clearfog Base

This is based on what I submitted upstream at
https://patchwork.ozlabs.org/patch/809838/ (which hasn't been merged
yet).

Change-Id: I6466ddfb10962d1d85f98aa4d45232f737f010e0
diff --git a/board/czechlight/clearfog/linux.fragment b/board/czechlight/clearfog/linux.fragment
new file mode 100644
index 0000000..b7ed5b0
--- /dev/null
+++ b/board/czechlight/clearfog/linux.fragment
@@ -0,0 +1 @@
+CONFIG_SENSORS_MCP3021=y