fdt: Sync up with libfdt

This brings in changes up to commit f9e91a48 in the libfdt repo.
Mostly this is whitespace/minor changes. But there are a few new
features:

- fdt_size_cells() and fdt_address_cells()
- fdt_resize()

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/lib/libfdt/fdt_rw.c b/lib/libfdt/fdt_rw.c
index 6fa4f13..bec8b8a 100644
--- a/lib/libfdt/fdt_rw.c
+++ b/lib/libfdt/fdt_rw.c
@@ -43,9 +43,9 @@
 
 #define FDT_RW_CHECK_HEADER(fdt) \
 	{ \
-		int err; \
-		if ((err = _fdt_rw_check_header(fdt)) != 0) \
-			return err; \
+		int __err; \
+		if ((__err = _fdt_rw_check_header(fdt)) != 0) \
+			return __err; \
 	}
 
 static inline int _fdt_data_size(void *fdt)