mkdtboimg: Sort imports

Change-Id: I9de99407d5b3feb0e9111d0af654e0e9607843f2
diff --git a/utils/src/mkdtboimg.py b/utils/src/mkdtboimg.py
index 136543f..66981eb 100755
--- a/utils/src/mkdtboimg.py
+++ b/utils/src/mkdtboimg.py
@@ -18,13 +18,13 @@
 """Tool for packing multiple DTB/DTBO files into a single image"""
 
 import argparse
-import os
 import fnmatch
+import os
+import struct
+import zlib
 from array import array
 from collections import namedtuple
-import struct
 from sys import stdout
-import zlib
 
 class CompressionFormat(object):
     """Enum representing DT compression format for a DT entry.