mkdtboimg: Sanitize dt filename

* Some vendors *again MTK* append the file sub-folder to filename.
  In these cases still use recursive search, but with the file
  basename

Change-Id: Ic6dc8c09e8f6ebcf8f5e8ea51edf893a7b695913
diff --git a/utils/src/mkdtboimg.py b/utils/src/mkdtboimg.py
index 136543f..614e582 100755
--- a/utils/src/mkdtboimg.py
+++ b/utils/src/mkdtboimg.py
@@ -900,7 +900,7 @@
         filepath = dt_arg['filename']
         if not os.path.isabs(filepath):
             for root, dirnames, filenames in os.walk(args.dtbdir):
-                for filename in fnmatch.filter(filenames, filepath):
+                for filename in fnmatch.filter(filenames, os.path.basename(filepath)):
                     filepath = os.path.join(root, filename)
         params['dt_file'] = open(filepath, 'rb')
         params['dt_offset'] = 0