binman: Allow unit addresses for binaries

Allow the same binary to appear multiple times in an image by using the
device-tree unit-address feature (u-boot@0, u-boot@1).

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/README b/tools/binman/README
index b200981..196dda1 100644
--- a/tools/binman/README
+++ b/tools/binman/README
@@ -387,6 +387,10 @@
 Examples of the above options can be found in the tests. See the
 tools/binman/test directory.
 
+It is possible to have the same binary appear multiple times in the image,
+either by using a unit number suffix (u-boot@0, u-boot@1) or by using a
+different name for each and specifying the type with the 'type' attribute.
+
 
 Special properties
 ------------------