binman: Create README.entries

Create a new README containing documentation for the entry types supported
by binman. This provides an easy reference in one place. It is
automatically generated from the source-code documentation.

Add a reference to this from the binman README.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/README b/tools/binman/README
index d60c7fd..cb34171 100644
--- a/tools/binman/README
+++ b/tools/binman/README
@@ -453,6 +453,15 @@
 	distinguish binaries with otherwise identical names.
 
 
+Entry Documentation
+-------------------
+
+For details on the various entry types supported by binman and how to use them,
+see README.entries. This is generated from the source code using:
+
+	binman -E >tools/binman/README.entries
+
+
 Special properties
 ------------------