wic: use items instead of iteritems

Dictionary method 'iteritems' doesn't exist in Python 3.
Replaced 'iteritems' with 'items' to be able to run the
code under both Python 3 and Python 2.

[YOCTO #9412]

(From OE-Core rev: 5b14eb8d68aaca82de4f8f6bcb28ad6f4a5125d0)

Signed-off-by: Ed Bartosh <ed.bartosh@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

scripts/lib/wic/creator.py

@@ -41,7 +41,7 @@ class Creator(object):
 
         # get cmds from pluginmgr
         # mix-in do_subcmd interface
-        for subcmd, klass in pluginmgr.get_plugins('imager').iteritems():
+        for subcmd, klass in pluginmgr.get_plugins('imager').items():
             if not hasattr(klass, 'do_create'):
                 msger.warning("Unsupported subcmd: %s" % subcmd)
                 continue