binman: Enhance the map and fdt-update output

At present the .map file produced for each image does not include the
overall image size. This is useful information.

Update the code to generate it in the .map file as well as the updated
FDT. Also fix a few comments while we are here.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/tools/binman/README b/tools/binman/README
index 5ff20f1..4b13776 100644
--- a/tools/binman/README
+++ b/tools/binman/README
@@ -584,10 +584,11 @@
 generates. This shows the offset and size of each entry. For example:
 
       Offset      Size  Name
-    00000000  00000010  section@0
-     00000000  00000004  u-boot
-    00000010  00000010  section@1
-     00000000  00000004  u-boot
+    00000000  00000028  main-section
+     00000000  00000010  section@0
+      00000000  00000004  u-boot
+     00000010  00000010  section@1
+      00000000  00000004  u-boot
 
 This shows a hierarchical image with two sections, each with a single entry. The
 offsets of the sections are absolute hex byte offsets within the image. The