dtoc: Allow the device tree to be compiled from source

If a source device tree is provide to the Fdt() constructors, compile it
automatically. This will be used in tests, where we want to build a
particular test .dts file and check that it works correctly in binman.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/dtoc/fdt_fallback.py b/tools/dtoc/fdt_fallback.py
index 5b0f2a1..f76f42a 100644
--- a/tools/dtoc/fdt_fallback.py
+++ b/tools/dtoc/fdt_fallback.py
@@ -80,6 +80,8 @@
 
     def __init__(self, fname):
         Fdt.__init__(self, fname)
+        if self._fname:
+            self._fname = fdt_util.EnsureCompiled(self._fname)
 
     def GetSubNodes(self, node):
         """Returns a list of sub-nodes of a given node