binman: Rename ExpandEntries to gen_entries

Leave the 'expand' term for use by entry types which have an expanded
version of themselves. Rename this method to indicate that it generates
subentries.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Alper Nebi Yasak <alpernebiyasak@gmail.com>
diff --git a/tools/binman/control.py b/tools/binman/control.py
index c9d7a08..d4c8dc8 100644
--- a/tools/binman/control.py
+++ b/tools/binman/control.py
@@ -507,7 +507,7 @@
     # entry offsets remain the same.
     for image in images.values():
         image.CollectBintools()
-        image.ExpandEntries()
+        image.gen_entries()
         if update_fdt:
             image.AddMissingProperties(True)
         image.ProcessFdt(dtb)