binman: Add a temporary hack for duplicate phandles

Three boards use a phandle in a FIT generator and the maintainer is
away. For now, add a hack to allow this.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/cmdline.py b/tools/binman/cmdline.py
index 9632ec1..39c61c2 100644
--- a/tools/binman/cmdline.py
+++ b/tools/binman/cmdline.py
@@ -126,6 +126,8 @@
             help='Comma-separated list of bintools to consider missing (for testing)')
     build_parser.add_argument('-i', '--image', type=str, action='append',
             help='Image filename to build (if not specified, build all)')
+    build_parser.add_argument('--ignore-dup-phandles', action='store_true',
+            help='Temporary option to ignore duplicate phandles')
     build_parser.add_argument('-I', '--indir', action='append',
             help='Add a path to the list of directories to use for input files')
     build_parser.add_argument('-m', '--map', action='store_true',