dtoc: Move the struct import into the correct order

This should be in with the other system includes. Move it.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/dtoc/dtoc.py b/tools/dtoc/dtoc.py
index ec80abe..e9ab46f 100755
--- a/tools/dtoc/dtoc.py
+++ b/tools/dtoc/dtoc.py
@@ -9,6 +9,7 @@
 import copy
 from optparse import OptionError, OptionParser
 import os
+import struct
 import sys
 
 import fdt_util
@@ -29,8 +30,6 @@
     from fdt_fallback import Fdt
     import fdt_fallback as fdt
 
-import struct
-
 # When we see these properties we ignore them - i.e. do not create a structure member
 PROP_IGNORE_LIST = [
     '#address-cells',