binman: Add special subnodes to the nodes generated by split-elf

Special nodes, hash and signature, is not being added to the nodes
generated for each segment in split-elf operation.

Copy the subnode logic used in _gen_fdt_nodes to _gen_split_elf to
ensure special nodes are added to the generated nodes.

Signed-off-by: Jonas Karlman <jonas@kwiboo.se>
Reviewed-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/entries.rst b/tools/binman/entries.rst
index 8f11189..78f95da 100644
--- a/tools/binman/entries.rst
+++ b/tools/binman/entries.rst
@@ -762,6 +762,9 @@
 
                 atf-bl31 {
                 };
+                hash {
+                    algo = "sha256";
+                };
             };
 
             @tee-SEQ {
@@ -777,6 +780,9 @@
 
                 tee-os {
                 };
+                hash {
+                    algo = "sha256";
+                };
             };
         };
 
@@ -805,6 +811,10 @@
             arch = "arm64";
             type = "firmware";
             description = "ARM Trusted Firmware";
+            hash {
+                algo = "sha256";
+                value = <...hash of first segment...>;
+            };
         };
         atf-2 {
             data = <...contents of second segment...>;
@@ -814,6 +824,10 @@
             arch = "arm64";
             type = "firmware";
             description = "ARM Trusted Firmware";
+            hash {
+                algo = "sha256";
+                value = <...hash of second segment...>;
+            };
         };
     };