pylibfdt: move pylibfdt to scripts/dtc/pylibfdt and refactor makefile

The pylibfdt is used by dtoc (and, indirectly by binman), but there
is no reason why it must be generated in the tools/ directory.

Recently, U-Boot switched over to the bundled DTC, and the directory
structure under scripts/dtc/ now mirrors the upstream DTC project.
So, scripts/dtc/pylibfdt is the best location.

I also rewrote the Makefile in a cleaner Kbuild style.

The scripts from the upstream have been moved as follows:

  lib/libfdt/pylibfdt/setup.py -> scripts/dtc/pylibfdt/setup.py
  lib/libfdt/pylibfdt/libfdt.i -> scripts/dtc/pylibfdt/libfdt.i_shipped

The .i_shipped is coped to .i during building because the .i must be
located in the objtree when we build it out of tree.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
diff --git a/scripts/dtc/pylibfdt/Makefile b/scripts/dtc/pylibfdt/Makefile
new file mode 100644
index 0000000..01d5e0f
--- /dev/null
+++ b/scripts/dtc/pylibfdt/Makefile
@@ -0,0 +1,30 @@
+# Unfortunately setup.py below cannot handle srctree being ".." which it often
+# is. It fails with an error like:
+# Fatal error: can't create build/temp.linux-x86_64-2.7/../lib/libfdt/fdt.o:
+#    No such file or directory
+# To fix this, use an absolute path.
+LIBFDT_srcdir = $(abspath $(srctree)/$(src)/../libfdt)
+
+include $(LIBFDT_srcdir)/Makefile.libfdt
+
+# Unfortunately setup.py (or actually the Python distutil implementation) puts
+# files into the same directory as the .i file. We cannot touch the source
+# directory, so we "ship" .i file into the objtree.
+PYLIBFDT_srcs = $(addprefix $(LIBFDT_srcdir)/,$(LIBFDT_SRCS)) \
+		$(obj)/libfdt.i
+
+quiet_cmd_pymod = PYMOD   $@
+      cmd_pymod = unset CC; unset CROSS_COMPILE; unset CFLAGS;\
+		LDFLAGS="$(HOSTLDFLAGS)" \
+		VERSION="u-boot-$(UBOOTVERSION)" \
+		CPPFLAGS="$(HOSTCFLAGS) -I$(LIBFDT_srcdir)" OBJDIR=$(obj) \
+		SOURCES="$(PYLIBFDT_srcs)" \
+		SWIG_OPTS="-I$(LIBFDT_srcdir) -I$(LIBFDT_srcdir)/.." \
+		$(PYTHON) $< --quiet build_ext --inplace
+
+$(obj)/_libfdt.so: $(src)/setup.py $(PYLIBFDT_srcs) FORCE
+	$(call if_changed,pymod)
+
+always += _libfdt.so
+
+clean-files += libfdt.i _libfdt.so libfdt.py libfdt_wrap.c