pylibfdt: Rename libfdt.swig to libfdt.i

The .i extension allows Python distutils to automatically handle the swig
file. Rename it.

Signed-off-by: Simon Glass <sjg@chromium.org>
Suggested-by: Mike Frysinger <vapier@gentoo.org>
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

pylibfdt/Makefile.pylibfdt

@@ -13,7 +13,7 @@ $(PYMODULE): $(PYLIBFDT_srcs) $(WRAP)
 	@$(VECHO) PYMOD $@
 	$(call run_setup, $^, build_ext --inplace)
 
-$(WRAP): $(PYLIBFDT_srcdir)/libfdt.swig
+$(WRAP): $(PYLIBFDT_srcdir)/libfdt.i
 	@$(VECHO) SWIG $@
 	$(SWIG) -python -o $@ $<